Interventions for increasing solid organ donor registration

Alvin H Li; Marcus Lo; Jacob E Crawshaw; Alexie J Dunnett; Kyla L Naylor; Amit X Garg; Justin Presseau

doi:10.1002/14651858.CD010829.pub2

. 2021 Apr 4;2021(4):CD010829. doi: 10.1002/14651858.CD010829.pub2

Interventions for increasing solid organ donor registration

Alvin H Li ^1,^✉, Marcus Lo ², Jacob E Crawshaw ³, Alexie J Dunnett ⁴, Kyla L Naylor ², Amit X Garg ⁵, Justin Presseau ³

Editor: Cochrane Kidney and Transplant Group

PMCID: PMC8164549 PMID: 35608942

Abstract

Background

A solution for increasing the number of available organs for transplantation is to encourage more individuals to register a commitment for deceased organ donation. However, the percentage of the population registered for organ donation remains low in many countries.

Objectives

To evaluate the benefits and harms of various interventions used to increase deceased organ donor registration.

Search methods

We searched the Cochrane Kidney and Transplant Register of Studies up to 11 August 2020 through contact with an Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register Search Portal and ClinicalTrials.gov.

Selection criteria

We included all randomised controlled trials (RCTs), cluster RCTs and quasi‐RCTs of interventions to promote deceased organ donor registration. We included studies if they measured self‐reported or verified donor registration, intention to donate, intention to register a decision or number of individuals signing donor cards as outcomes.

Data collection and analysis

Two authors independently assessed retrieved studies and extracted data from included studies. We assessed studies for risk of bias. We obtained summary estimates of effect using a random‐effects model and expressed results as risk ratios (RR) (95% confidence intervals; CI) for dichotomous outcomes and mean difference (MD; 95% CI) or standardised mean difference (SMD; 95% CI) for continuous outcomes. In multi‐arm trials, data were pooled to create single pair‐wise comparisons. Analyses were stratified by specific intervention setting where available.

Main results

Our search strategy identified 46 studies (47 primary articles, including one abstract) comprising 24 parallel RCTs, 19 cluster RCTs and 3 quasi‐RCTs. Sample sizes ranged from 138 to 1,085,292 (median = 514). A total of 16 studies measured registration behaviour, 27 measured intention to register/donate and three studies measured both registration behaviour and intention to register.

Interventions were delivered in a variety of different settings: schools (14 studies), driver’s motor vehicle (DMV) centres (5), mail‐outs (4), primary care centres (3), workplaces (1), community settings (7) and general public (12). Interventions were highly varied in terms of their content and included strategies such as educational sessions and videos, leveraging peer leaders, staff training, message framing, and priming. Most studies were rated as having high or unclear risk of bias for random sequence generation and allocation concealment and low risk for the remainder of the domains.

Data from 34/46 studies (74%) were available for meta‐analysis. Low certainty evidence showed organ donation registration interventions had a small overall effect on improving registration behaviour (16 studies, 1,294,065 participants: RR 1.30, 95% CI 1.19 to 1.43, I² = 84%), intention to register/donate (dichotomous) (10 studies, 10,838 participants: RR 1.21, 95% CI 1.03 to 1.42, I² = 91%) and intention to register/donate (continuous) (9 studies, 3572 participants: SMD 0.23, 95% CI 0.11 to 0.36, I² = 67%).

Classroom‐based interventions delivered in a lecture format by individuals from the transplant community may be effective at increasing intention to register/donate (3 studies, 675 participants: RR 1.33, 95% CI 1.15 to 1.55, I² = 0%). Community interventions targeting specific ethnic groups were generally effective at increasing registration rates (k = 5, n = 4186; RR 2.14, 95% CI 1.35 to 3.40, I² = 85%), although heterogeneity was high. In particular, interventions delivered in the community by trained peer‐leaders appear to be effective (3 studies, 3819 participant: RR 2.09, 95% CI 1.08 to 4.06, I² = 87%), although again, the data lacked robustness. There was some evidence that framing messages (e.g. anticipated regret) and priming individuals (e.g. reciprocity) in a certain way may increase intention to register/donate, however, few studies measured this effect on actual registration.

Overall, the studies varied significantly in terms of design, setting, content and delivery. Selection bias was evident and a quarter of the studies could not be included in the meta‐analysis due to incomplete outcome data reporting. No adverse events were reported.

Authors' conclusions

In our review, we identified a variety of approaches used to increase organ donor registration including school‐based educational sessions and videos, leveraging peer leaders in the community, DMV staff training, targeted messaging and priming. The variability in outcome measures used and incompleteness in reporting meant that most data could not be combined for analysis. When data were combined, overall effect sizes were small in favour of intervention groups over controls, however, there was significant variability in the data. There was some evidence that leveraging peer‐leaders in the community to deliver organ donation education may improve registration rates and classroom‐based education from credible individuals (i.e. members of the transplant community) may improve intention to register/donate, however, there is no clear evidence favouring any particular approach. There was mixed evidence for simple, low‐intensity interventions utilising message framing and priming. However, it is likely that interest in these strategies will persist due to their reach and scalability. Further research is therefore required to adequately address the question of the most effective interventions for increasing deceased organ donor registration.

Plain language summary

Interventions for increasing solid organ donor registration

What is the issue?

There is a global need to increase the number of available organs for transplantation. One possible strategy is to encourage more individuals to register as organ donors.

What did we do?

To address this, we identified 46 studies that tested various strategies to encourage people to register as an organ donor. Sixteen of these studies measured actual registration, 27 studies measured people’s intention to register/donate and three studies measured both.

What did we find?

Studies were conducted in widely different settings including schools, driver motor vehicle (DMV) centres, primary care and in the local community. Studies also used widely different strategies to increase registration such as education, training peer‐leaders, training DMV or primary care staff, and framing information about organ donation in certain ways.

We found that studies had a small overall effect on people’s intention to register/donate along with actual registration rates, however, no particular strategy stood out as being more effective than the rest. There was encouraging evidence that training peer‐leaders in the community to deliver organ donation education may improve registration rates and classroom‐based education from members of the transplant community may improve intention to register/donate. There was also some evidence that framing organ donation information in certain ways may help increase people’s intention to register/donate but further studies are needed.

Conclusions

In summary, strategies to increase organ donation registration have some benefit but vary considerably in terms of the setting in which they are delivered, who they target and how they are delivered.

Summary of findings

Background

Description of the condition

Many patients worldwide are dying on the transplant waiting list due to the shortage of available organs (Aubrey 2008; Santiago‐Delpin 1997; Van Gelder 2008; Wolfe 2010). One potential solution for increasing the number of available organs for transplantation is to develop interventions to support and encourage individuals to register a commitment for deceased organ donation through a registry (Rosenblum 2012). Despite support for donor registries from the public and national organisations, many countries have modest registration rates (< 40% of the population registered) (Rosenblum 2012). Thus, while establishing the donor registry infrastructure is necessary, it is not a sufficient intervention for ensuring that individuals actually register their donation wishes.

Description of the intervention

As of 2012, 19 countries operated deceased organ donor registries where the stated goal is to maximise the total number of affirmative registrants (Rosenblum 2012). These registries are used to communicate an individual’s wish regarding organ donation after death to their next‐of‐kin. Registration choices differ among nations, and can include “yes” only, “yes and no” and “yes, no and unsure”. In addition, some countries also allow individuals to clarify which organs and tissues they wish to donate. Past studies have found that families are more likely to consent to organ donation if their loved ones had previously expressed a willingness to donate (e.g. on a donor card or driver’s license) (Lawlor 2006; Siminoff 2002).

How the intervention might work

Many interventions can effectively increase knowledge, attitude and prompt family discussion about organ donation (Li 2013a). These interventions can include mass media campaigns and classroom educational programs. Such interventions have been shown to benefit other public health issues such as drinking and driving (Elder 2004) and smoking (Bala 2017). However, it is unclear which interventions have actually demonstrated an increase in the number of individuals registering a commitment to organ donation (Li 2013a; Thornton 2012). Surveys have further found that while a majority of respondents were willing to be donors, many had not registered (Lee 2010; Yeung 2000). The gap between willingness to be a donor and actual registration may be due to a lack of awareness of the registry, uncertainty about the registration process or perceived ineligibility as a donor amongst other things (Li 2017; Siegel 2005; Yeung 2000).

Why it is important to do this review

The need for interventions that go beyond merely increasing support for organ donation, but increase actual affirmative registration values, prompted the present review. Moreover, there is a need to identify the best quality evidence (e.g. randomised controlled trials (RCTs)) which was a limitation of previous reviews in this area (Golding 2017; Jones 2017; Li 2013a; Li 2015). This systematic review synthesises the best evidence currently available from studies evaluating various interventions to increase affirmative organ donor registrants. This review aims to guide the design and use of further interventions to fill organ donor registries. The focus of this review is on solid organ donations after death. Interventions may benefit society if an increased number of organ donor registrants directly translates to an increased number of deceased donors. However, it is important to keep in mind that these interventions may also be detrimental to society or individual participants if they unintentionally discourage registration for deceased organ donation.

Objectives

This review aims to look at the benefits and harms of various interventions used to increase deceased organ donor registration.

Methods

Criteria for considering studies for this review

Types of studies

We included all RCTs, quasi‐RCTs (RCTs in which allocation to treatment was obtained by alternation, use of alternate medical records, date of birth or other predictable methods), and cluster RCTs that evaluated interventions to promote deceased organ donor registration. We had planned to include controlled before‐after studies, but we subsequently decided to focus on RCTs because of their lower risk of bias. We excluded studies from countries that do not comply with the Declaration of Istanbul.

Types of participants

Inclusion criteria

All participants eligible to make a commitment for deceased organ donation in their respective jurisdiction.

Exclusion criteria

Participants who are not eligible to register for deceased organ donation in their respective jurisdiction (e.g. under the minimum age required).

We excluded studies that examined consent for organ donation from relatives of patients declared deceased and eligible for organ donation. We also excluded studies focusing on increasing living organ donation.

Types of interventions

We considered any interventions and methods of delivering an intervention used to increase organ donor registration including classroom educational program, brochures, interactive computer program, videos, and multi‐component interventions. The comparison group could be an inactive control intervention (e.g. no intervention) or an active intervention (e.g. different variant of an educational program). We excluded interventions solely focusing on tissue or blood donation.

Types of outcome measures

Characteristics of joining an organ donor registry vary among countries. We included studies that measured consent to deceased organ donation through registration in an organ donor registry, signed donor cards or verification of organ donation registration as shown on a driver’s licence or identification card. For this reason, we expected that identified studies would stem from countries with an explicit consent or "opt‐in" system. Registration choices may also be measured and may include "yes" (the participant declares that they would like to be a deceased organ donor in the advent of death), "no" and "unsure". We also included studies that measured self‐reported intention or willingness to become an organ donor. Furthermore, we extracted any adverse events reported in any studies. Adverse events may include discomfort or dissatisfaction with the intervention.

Primary outcomes

Registration in an organ donor registry (yes/no) and registration choices ("yes" to being a donor, "no" or "unsure")
Signed donor cards (yes/no)
Verification of organ donation as shown on driver's licence or identification card (yes/no)
Any adverse events. (e.g. discomfort with the intervention)

Secondary outcomes

Self‐reported intention to register as a donor (e.g. Do you intend to register as a donor?)
Self‐reported willingness to donation (e.g. Would you be willing to donate your organs?)

These can be either reported as yes/no or on a scale (e.g. yes/no/maybe, fully agree to fully disagree).

Search methods for identification of studies

Electronic searches

We searched the Cochrane Kidney and Transplant Register of Studies up to 11 August 2020 through contact with the Information Specialist using search terms relevant to this review. The Register contains studies identified from the following sources:

Monthly searches of the Cochrane Central Register of Controlled Trials (CENTRAL)
Weekly searches of MEDLINE OVID SP
Hand searching of kidney‐related journals and the proceedings of major kidney conferences
Searching of the current year of EMBASE OVID SP
Weekly current awareness alerts for selected kidney and transplant journals
Searches of the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov

Studies contained in the Register of Studies are identified through search strategies for CENTRAL, MEDLINE, and EMBASE based on the scope of Cochrane Kidney and Transplant. Details of these strategies, as well as a list of hand‐searched journals, conference proceedings, and current awareness alerts, are available in the Specialised Register section of information about Cochrane Kidney and Transplant.

See Appendix 1 for search terms used in strategies for this review.

Searching other resources

Reference lists of review articles, relevant studies, and clinical practice guideline

Data collection and analysis

Selection of studies

The search strategy described was used to obtain titles and abstracts of studies that may be relevant to the review. The titles and abstracts were screened independently by two authors, who discarded studies that clearly did not meet our inclusion criteria; studies and reviews that might include relevant data or information on studies were retained for full‐text screening.

Data extraction and management

Data extraction was carried out independently by two authors using data extraction forms. Where more than one publication of one study existed, we grouped reports together and the publication with the most complete data was extracted. For each study, we extracted relevant background information to provide context regarding its country's organ donor legislation.

Assessment of risk of bias in included studies

The following items were independently assessed by two authors using the risk of bias assessment tool (Higgins 2011) (see Appendix 2).

Was there adequate sequence generation (selection bias)?
Was allocation adequately concealed (selection bias)?
Was knowledge of the allocated interventions adequately prevented during the study (detection bias)?
- Participants and personnel
- Outcome assessors
Were incomplete outcome data adequately addressed (attrition bias)?
Are reports of the study free of suggestion of selective outcome reporting (reporting bias)?
Was the study apparently free of other problems that could put it at a risk of bias?

Measures of treatment effect

For dichotomous outcomes (e.g. donor registration status; yes/no) we expressed results as a risk ratio (RR) with 95% confidence intervals (CI). Where continuous scales of measurement are used to assess the effects of treatment (e.g. a scale of willingness to register as a donor), the mean difference (MD) was used, or the standardised mean difference (SMD) in the case of different scales being used.

Unit of analysis issues

We handled issues with non‐standard designs such as cluster RCTs as recommended by the Cochrane Handbook for Systematic Interventions (Higgins 2011). We estimated the effective sample size by dividing the original sample size by the design effect (1 + (Average Cluster Size ‐1) * intraclass correlation coefficient). We used the ICC reported in the study where available. If not reported, we used an intraclass coefficient (ICC) estimate of 0.07 based on a previous study (Li 2017). For dichotomous outcomes, both numbers of participants and numbers of participants registered for organ donation were divided by the design effect.

Dealing with missing data

If needed, any further information from the original author was requested by written correspondence (e.g. emailing or writing to corresponding author) and any relevant information obtained in this manner was included in the review. Attrition rates due to drop‐outs, losses to follow‐up, and withdrawals were investigated. Issues of missing data and imputation methods (e.g. last‐observation‐carried‐forward) were critically appraised (Higgins 2011).

Assessment of heterogeneity

Where applicable, we assessed heterogeneity using a Chi² test on N‐1 degrees of freedom, with an alpha of 0.05 used for statistical significance and with the I² test (Higgins 2003). I² values of 25%, 50% and 75% correspond to low, medium, and high levels of heterogeneity.

Assessment of reporting biases

If applicable, we used funnel plots to explore the potential existence of small study bias due to the large heterogeneity of the interventions (Higgins 2011).

Data synthesis

We pooled data using the random‐effects model and used the fixed‐effect model to ensure robustness of the model chosen and susceptibility to outliers where possible. In studies with multiple intervention groups, groups were combined to create a single pair‐wise comparison to ensure that no data were lost. For dichotomous outcomes, both the sample sizes and the number of people with events (registered/intended to register) were summed across groups. For continuous outcomes, pooled sample sizes, means and standard deviations were calculated.

Subgroup analysis and investigation of heterogeneity

We planned a subgroup analysis to explore possible sources of heterogeneity (e.g. participants, interventions and study quality). Heterogeneity among participants could be related to age, gender, educational level, or ethnicity. Heterogeneity in organ donor interventions may be related to the personnel delivering the intervention (e.g. volunteers, health care workers or transplant recipients), duration and method of delivery of the intervention (e.g. educational program, videos). We described any adverse effects that were reported by the authors. Adverse events may include discomfort or dissatisfaction with the intervention. Where possible, the risk difference with 95% CI was calculated for each adverse effect, either compared to no intervention or to another intervention. Due to the low number of studies identified comparing the same intervention and control, we were unable to perform subgroup analysis to explore possible sources of heterogeneity.

Sensitivity analysis

We planned to perform the following sensitivity analyses in order to explore the influence of the following factors on effect size.

Repeating the analysis excluding unpublished studies
Repeating the analysis taking account of risk of bias
Repeating the analysis excluding any very long or large studies to establish how much they dominate the results
Repeating the analysis excluding studies using the following filters: diagnostic criteria, language of publication, source of funding (industry versus other), and country

However, due to the wide variety of interventions, these were not possible.

Summary of findings and assessment of the certainty of the evidence

We produced Summary of Findings tables to determine the pooled effect of organ donation registration interventions on our primary (registration behaviour) and secondary outcomes (intention to register/donate). Separate analyses were done for dichotomous and continuous outcomes. Certainty of the evidence was assessed using GRADE.

Results

Description of studies

Results of the search

Our search strategy identified 115 potentially relevant records (see Figure 1). Six records were identified as ongoing studies/abstract only. After full text review from our search strategy, we included 47 records describing 46 RCTs that met our inclusion criteria. One study was included but no full text publication was available (Dobbels 2009). The six ongoing studies will be incorporated in a future update of this review (ACTRN12614000690651; Andrews 2012a; iDecide 2010; NCT02318849; RegisterNow‐1 2017; Yee 2014).

Included studies

See Characteristics of included studies table.

We included 24 parallel RCTs (52%), 19 cluster RCTs(41%), and 3 quasi‐RCTs (6.7%). Most studies had 2 arms (29 studies; 63%), followed by 4 arms (8 studies; 17%), 3 arms (7 studies, 15%), one study with 6 arms, and one study had 8 arms. The number of clusters in the 19 cluster RCTs ranged from 9 to 121. Four (21%) cluster RCTs did not report the number of clusters included in their study. The sample size of participants for all included studies ranged from 138 to 1,085,292 (median: 514). Four studies did not report a total sample size (Alvaro 2011a; Alvaro 2011b; Rodrigue 2012; Rodrigue 2015).

Studies were conducted in the USA (23 studies; 50%), the UK (8 studies; 17%), and the Netherlands (6 studies; 13%). One international study was conducted in Australia, Belgium, Brazil, Ireland, Spain, and Taiwan.

Outcomes measured

A total of 16 studies measured registration behaviour (Alvaro 2011a; Alvaro 2011b; Andrews 2012; Bidigare 2000; Degenholtz 2015; Degenholtz 2019; Loughery 2017; INORDAR 2012; Quick 2012; Quick 2015; Resnicow 2010; Rodrigue 2012; Rodrigue 2015; Sallis 2018; Thornton 2012; Thornton 2016), 27 studies measured intention to register/donate (Alarcon 2008; Blazek 2018; Cardenas 2010; Chien 2015; Dobbels 2009; Doherty 2017; Doyle 2019a; Doyle 2019b; Hirai 2020; O'Carroll 2011a; O'Carroll 2011b; O'Carroll 2017a; O'Carroll 2017b; O'Carroll 2019; Project ACTS I 2010; Project ACTS II 2013; Quinn 2006; Reubsaet 2003; Reubsaet 2004a; Reubsaet 2004b; Reubsaet 2005; Riccetto 2019; Siegel 2016; Skumanich 1996; Smits 2006; Steenaart 2018; Thornton 2019) and three studies measured both registration behaviour and intention to register (Hyde 2013; Murakami 2016; Rodrigue 2019).

A total of 14 studies reported actual registration rates as verified by the donor registry (Andrews 2012; Degenholtz 2015; Degenholtz 2019; Loughery 2017; INORDAR 2012; Quick 2012; Quick 2015; Resnicow 2010; Rodrigue 2012; Rodrigue 2015; Rodrigue 2019; Sallis 2018; Thornton 2012; Thornton 2016). Five studies reported either the number of signed cards or forms returned (Alvaro 2011a; Alvaro 2011b), self‐reported registration (Hyde 2013; Murakami 2016) or self‐reported making a decision to donate (Bidigare 2000).

Among studies measuring intention, 18 studies measured intention to register to donate (e.g. do you intend to register as a donor?) as the outcome measure (Blazek 2018; Chien 2015; Dobbels 2009; Doyle 2019a; Doyle 2019b; Hirai 2020; Hyde 2013; Quinn 2006; Reubsaet 2003; Reubsaet 2004a; Reubsaet 2004b; Reubsaet 2005; Riccetto 2019; Rodrigue 2019; Siegel 2016; Skumanich 1996; Steenaart 2018; Thornton 2019). Eight studies measured intention to donate (e.g. do you intend to donate your organs?) as the outcome measure (Alarcon 2008; Doherty 2017; Murakami 2016; O'Carroll 2011a; O'Carroll 2011b; O'Carroll 2017a; O'Carroll 2017b; O'Carroll 2019). Two studies measured participants readiness to express donation intentions via a driver’s license, donor card and/or discussions with family members (Project ACTS I 2010, Project ACTS II 2013). Two studies measured willingness to donate (e.g. would you be willing to be a donor?) without asking any questions focusing on registering for donation (Cardenas 2010; Smits 2006).

Excluded studies

We excluded 34 studies from our review (see Characteristics of excluded studies). Studies were excluded for being unrelated to deceased organ donation (23 studies) or they focused on general attitudes towards organ donation and did not measure organ donor registration behaviours (11 studies).

Risk of bias in included studies

See Characteristics of included studies table for an assessment of the risk of bias of the included studies (see Figure 2; Figure 3). Overall, the majority of studies were rated as having high or unclear risk of bias.

Risk of bias summary: review authors' judgements about each risk of bias item for each included study.

Risk of bias graph: review authors' judgements about each risk of bias item presented as percentages across all included studies.

Allocation

Random sequence generation

Twenty‐one studies (43%) did not report their method of sequence generation. Among those studies with a low risk of bias (22; 48%), the random sequence generation methods included: online randomisation tool (Project ACTS II 2013), coin flip (Alvaro 2011a, Cardenas 2010; Degenholtz 2015), computer‐generated sequence (Doherty 2017; Hyde 2013; Murakami 2016; Thornton 2016; Steenaart 2018), random number table (Thornton 2012), and a third‐party company to perform the simple randomisation (INORDAR 2012; Thornton 2019).

Allocation concealment

Twenty‐nine studies did not report their method of allocation concealment or had a high risk bias (63%). Among the 13 studies with low risk of bias, the method of allocation concealment included using sealed envelopes (Thornton 2012; Thornton 2016; Rodrigue 2019).

Blinding

Performance bias

Twenty‐one studies (46%) were reported as having a low risk of performance bias. Blinding of participants and study personnel was not addressed in many studies. However, due to the nature of the study design of some of these studies (e.g. cluster randomisation at the classroom level), participants may likely have been aware of which groups (intervention or control) they were assigned, to which may have caused them to respond to the intervention accordingly.

Detection bias

Forty‐four studies (93%) were assessed as low risk of bias, given that the outcome (e.g. intention to register for organ donation) was either measured via self‐report or through actual registration rates. We judged two studies that reported using a non‐blinded interviewer to ask participants about their intention to register to be at high risk of bias (Doherty 2017; Doyle 2019a).

Incomplete outcome data

Four studies (9%) were judged to be at high risk of attrition bias because they reported high loss to follow‐up rates, and stated that those who completed the study had different characteristics than those that were lost to follow‐up (Project ACTS II 2013; Hyde 2013; Loughery 2017; Quinn 2006).

Selective reporting

Thirty‐six studies (78%) were deemed to be at low risk of reporting bias. Ten studies (22%) were assessed as high risk of bias. These studies did not report a numerator or denominator for the outcomes considered in this review (Alarcon 2008; Bidigare 2000; Dobbels 2009; Hyde 2013; Project ACTS II 2013; Reubsaet 2004a; Reubsaet 2004b; Rodrigue 2012; Rodrigue 2015; Skumanich 1996).

Other potential sources of bias

Nineteen studies (41%) were deemed to be at unclear or high risk of other bias. The most common source of other bias were biases associated were not reporting baseline differences.

Effects of interventions

See: Table 1; Table 2; Table 3

Summary of findings 1. Summary of Findings Table ‐ Interventions for increasing solid organ donation registration (dichotomous outcome).

Interventions for increasing solid organ donation registration (dichotomous outcome)
Patient or population: increasing solid organ donation registration Setting: Intervention: intervention Comparison: control
Outcomes	*Anticipated absolute effects^ (95% CI)**		Relative effect (95% CI)	№ of participants  (studies)	Certainty of the evidence (GRADE)	Comments
	Risk with control	Risk with intervention
Registration behaviour: ICC adjusted (dichotomous)	40 per 1,000	52 per 1,000 (47 to 57)	RR 1.30 (1.19 to 1.43)	1294065 (16 RCTs)	⊕⊕⊝⊝ LOW ^a,^b,^c
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).   CI: Confidence interval; RR: Risk ratio
GRADE Working Group grades of evidence High certainty: We are very confident that the true effect lies close to that of the estimate of the effect Moderate certainty: We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different Low certainty: Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect Very low certainty: We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect
See interactive version of this table: https://gdt.gradepro.org/presentations/#/isof/isof_question_revman_web_416986025065372155.

Study	In‐person Ed	Video Ed	Web Ed	Framing	Peer leaders	Priming	S.I.M	Staff training	Planning/rehearsal
Alarcon 2008	X	X	‐	‐	‐	‐	‐	‐	‐
Alvaro 2011a	X	‐	‐	‐	‐	‐	‐	‐	‐
Alvaro 2011b	X	‐	‐	X	‐	‐	‐	‐	‐
Andrews 2012	X	X	‐	‐	X	‐	‐	‐	‐
Bidigare 2000	X	‐	‐	‐	‐	‐	‐	‐	‐
Blazek 2018	‐	‐	‐	‐	‐	X	‐	‐	‐
Cardenas 2010	X	‐	‐	‐	X	‐	‐	‐	‐
Chien 2015	‐	‐	‐	X	‐	‐	‐	‐	‐
Degenholtz 2015	‐	‐	X	‐	‐	‐	‐	X	‐
Degenholtz 2019	X	‐	X	‐	‐	‐	‐	X	‐
Dobbels 2009	X	‐	‐	‐	‐	‐	‐	‐	‐
Doherty 2017	‐	‐	‐	‐	‐	‐	X	‐	‐
Doyle 2019a	‐	‐	‐	‐	‐	‐	X	‐	‐
Doyle 2019b	‐	‐	‐	‐	‐	‐	X	‐	‐
Hirai 2020	‐	‐	‐	X	‐	‐	‐	‐	‐
Hyde 2013	‐	‐	X	‐	‐	‐	‐	‐	X
INORDAR 2012	‐	‐	‐	‐	‐	‐	X	‐	‐
Loughery 2017	X	X	‐	‐	X	‐	‐	‐	‐
Murakami 2016	X	‐	‐	‐	‐	‐	‐	‐	‐
O'Carroll 2011a	‐	‐	‐	‐	‐	‐	X	‐	‐
O'Carroll 2011b	‐	‐	‐	‐	‐	‐	X	‐	‐
O'Carroll 2017a	‐	‐	‐	‐	‐	X	X	‐	‐
O'Carroll 2017b	‐	‐	‐	‐	‐	X	X	‐	‐
O'Carroll 2019	‐	‐	‐	‐	‐	X	X	‐	‐
Project ACTS 1 2010	‐	X	‐	‐	‐	‐	‐	‐	‐
Project ACTS II 2013	X	X	‐	‐	‐	‐	‐	‐	‐
Quick 2012	‐	‐	‐	X	‐	‐	‐	‐	‐
Quick 2015	‐	‐	‐	X	‐	‐	‐	‐	‐
Quinn 2006	X	‐	‐	‐	‐	‐	‐	‐	‐
Resnicow 2010	X	‐	‐	‐	X	‐	‐	‐	‐
Reubsaet 2003	‐	‐	‐	‐	‐	‐	‐	‐	X
Reubsaet 2004a	X	X	‐	‐	‐	‐	‐	‐	‐
Reubsaet 2004b	‐	‐	X	‐	‐	‐	‐	‐	‐
Reubsaet 2005	‐	X	X	‐	‐	‐	‐	‐	X
Riccetto 2019	‐	‐	X	‐	‐	‐	‐	‐	‐
Rodrigue 2012	X	‐	‐	‐	‐	‐	‐	X	‐
Rodrigue 2015	‐	X	‐	‐	‐	‐	‐	‐	‐
Rodrigue 2019	‐	X	‐	‐	‐	‐	‐	‐	‐
Sallis 2018	‐	‐	‐	X	‐	‐	‐	‐	‐
Siegel 2016	‐	‐	‐	‐	‐	X	‐	‐	‐
Skumanich 1996	X	‐	‐	‐	‐	‐	‐	‐	‐
Smits 2006	X	‐	‐	‐	‐	‐	‐	‐	‐
Steenaart 2019	X	X	‐	‐	‐	‐	‐	‐	X
Thornton 2012	‐	X	‐	‐	‐	‐	‐	‐	‐
Thornton 2016	‐	X	‐	‐	‐	‐	‐	‐	‐
Thornton 2019	‐	X	‐	‐	‐	‐	‐	‐	‐
Total	18	13	6	6	4	5	9	3	4

Database	Search terms
CENTRAL	MeSH descriptor: [Tissue and Organ Procurement] this term only ((tissue or organ or organs) next donor):ti,ab,kw ((tissue or organ or organs) near donat):ti,ab,kw (deceased next donor):ti,ab,kw {or #1‐#4} (register or registers):ti,ab,kw (registry or registries):ti,ab,kw registrant:ti,ab,kw registration:ti,ab,kw "Attitude to health":kw ((willingness or intention or opinion or opinions or attitude) near (donat or donor*)):ti,ab (donor designation):ti,ab,kw {or #6‐#12} {and #5, #13}
MEDLINE	Tissue Donors/ "Tissue and Organ Procurement"/ Organ Transplantation/ (organ donor* or tissue donor).tw. ((organ or organs or tissue) adj3 donat).tw. deceased donor.tw. or/1‐6 Registries/ (register or registers).tw. (registry or registries).tw. registrant.tw. registration.tw. "Attitude to Health"/ ((willingness or intention or opinion or opinions or attitude) adj10 (donat or donor*)).tw. donor designation.tw. or/8‐15 and/7,16
EMBASE	organ donor/ directed tissue donation/ organ transplantation/ (organ donor* or tissue donor).tw. ((organ or organs or tissue) adj3 donat).tw. deceased donor.tw. or/1‐6 registry/ registration/ (register or registers).tw. (registry or registries).tw. registrant.tw. registration.tw. "attitude to health"/ ((willingness or intention or opinion or opinions or attitude) adj10 (donat or donor*)).tw. donor designation.tw. or/8‐16 and/7,17
CINAHL	(MH "Tissue and Organ Harvesting+") (MH "Living Donors") (MH "Organ Transplantation+") (MH "Organ Procurement+") TI organ donor* AB organ donor* TI tissue donor* AB tissue donor* TI deceased donor* AB deceased donor* (MH "Organ Procurement+") OR/1‐11 (MM "Organ Donor Cards") TI register* AB register* TI registry AB registry TI registries AB registries TI registrant* AB registrant* TI registration* AB registration* (MM "Health Beliefs") (MM "Attitude to Health") TI donor designation AB donor designation willingness N5 (donor* or donat) intention N5 (donor or donat) attitude N5 (donor or donat) opinion N5 (donor* or donat*) OR/13‐31 AND/12,32

Potential source of bias	Assessment criteria
Random sequence generation Selection bias (biased allocation to interventions) due to inadequate generation of a randomised sequence	Low risk of bias: Random number table; computer random number generator; coin tossing; shuffling cards or envelopes; throwing dice; drawing of lots; minimization (minimization may be implemented without a random element, and this is considered to be equivalent to being random).
	High risk of bias: Sequence generated by odd or even date of birth; date (or day) of admission; sequence generated by hospital or clinic record number; allocation by judgement of the clinician; by preference of the participant; based on the results of a laboratory test or a series of tests; by availability of the intervention.
	Unclear: Insufficient information about the sequence generation process to permit judgement.
Allocation concealment Selection bias (biased allocation to interventions) due to inadequate concealment of allocations prior to assignment	Low risk of bias: Randomisation method described that would not allow investigator/participant to know or influence intervention group before eligible participant entered in the study (e.g. central allocation, including telephone, web‐based, and pharmacy‐controlled, randomisation; sequentially numbered drug containers of identical appearance; sequentially numbered, opaque, sealed envelopes).
	High risk of bias: Using an open random allocation schedule (e.g. a list of random numbers); assignment envelopes were used without appropriate safeguards (e.g. if envelopes were unsealed or non‐opaque or not sequentially numbered); alternation or rotation; date of birth; case record number; any other explicitly unconcealed procedure.
	Unclear: Randomisation stated but no information on method used is available.
Blinding of participants and personnel Performance bias due to knowledge of the allocated interventions by participants and personnel during the study	Low risk of bias: No blinding or incomplete blinding, but the review authors judge that the outcome is not likely to be influenced by lack of blinding; blinding of participants and key study personnel ensured, and unlikely that the blinding could have been broken.
	High risk of bias: No blinding or incomplete blinding, and the outcome is likely to be influenced by lack of blinding; blinding of key study participants and personnel attempted, but likely that the blinding could have been broken, and the outcome is likely to be influenced by lack of blinding.
	Unclear: Insufficient information to permit judgement
Blinding of outcome assessment Detection bias due to knowledge of the allocated interventions by outcome assessors.	Low risk of bias: No blinding of outcome assessment, but the review authors judge that the outcome measurement is not likely to be influenced by lack of blinding; blinding of outcome assessment ensured, and unlikely that the blinding could have been broken.
	High risk of bias: No blinding of outcome assessment, and the outcome measurement is likely to be influenced by lack of blinding; blinding of outcome assessment, but likely that the blinding could have been broken, and the outcome measurement is likely to be influenced by lack of blinding.
	Unclear: Insufficient information to permit judgement
Incomplete outcome data Attrition bias due to amount, nature or handling of incomplete outcome data.	Low risk of bias: No missing outcome data; reasons for missing outcome data unlikely to be related to true outcome (for survival data, censoring unlikely to be introducing bias); missing outcome data balanced in numbers across intervention groups, with similar reasons for missing data across groups; for dichotomous outcome data, the proportion of missing outcomes compared with observed event risk not enough to have a clinically relevant impact on the intervention effect estimate; for continuous outcome data, plausible effect size (difference in means or standardized difference in means) among missing outcomes not enough to have a clinically relevant impact on observed effect size; missing data have been imputed using appropriate methods.
	High risk of bias: Reason for missing outcome data likely to be related to true outcome, with either imbalance in numbers or reasons for missing data across intervention groups; for dichotomous outcome data, the proportion of missing outcomes compared with observed event risk enough to induce clinically relevant bias in intervention effect estimate; for continuous outcome data, plausible effect size (difference in means or standardized difference in means) among missing outcomes enough to induce clinically relevant bias in observed effect size; ‘as‐treated’ analysis done with substantial departure of the intervention received from that assigned at randomisation; potentially inappropriate application of simple imputation.
	Unclear: Insufficient information to permit judgement
Selective reporting Reporting bias due to selective outcome reporting	Low risk of bias: The study protocol is available and all of the study’s pre‐specified (primary and secondary) outcomes that are of interest in the review have been reported in the pre‐specified way; the study protocol is not available but it is clear that the published reports include all expected outcomes, including those that were pre‐specified (convincing text of this nature may be uncommon).
	High risk of bias: Not all of the study’s pre‐specified primary outcomes have been reported; one or more primary outcomes is reported using measurements, analysis methods or subsets of the data (e.g. subscales) that were not pre‐specified; one or more reported primary outcomes were not pre‐specified (unless clear justification for their reporting is provided, such as an unexpected adverse effect); one or more outcomes of interest in the review are reported incompletely so that they cannot be entered in a meta‐analysis; the study report fails to include results for a key outcome that would be expected to have been reported for such a study.
	Unclear: Insufficient information to permit judgement
Other bias Bias due to problems not covered elsewhere in the table	Low risk of bias: The study appears to be free of other sources of bias.
	High risk of bias: Had a potential source of bias related to the specific study design used; stopped early due to some data‐dependent process (including a formal‐stopping rule); had extreme baseline imbalance; has been claimed to have been fraudulent; had some other problem.
	Unclear: Insufficient information to assess whether an important risk of bias exists; insufficient rationale or evidence that an identified problem will introduce bias.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1.1 Registration behaviour: ICC adjusted (dichotomous)	16	1.294065E6	Risk Ratio (M‐H, Random, 95% CI)	1.30 [1.19, 1.43]
1.2 Registration behaviour (dichotomous): primary care setting (ICC adjusted)	3	3829	Risk Ratio (M‐H, Random, 95% CI)	1.13 [0.79, 1.61]
1.3 Registration behaviour (dichotomous): community setting (ICC adjusted)	5	4186	Risk Ratio (M‐H, Random, 95% CI)	2.14 [1.35, 3.40]

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
2.1 Registration intention: ICC adjusted (dichotomous)	10	10838	Risk Ratio (M‐H, Random, 95% CI)	1.21 [1.03, 1.42]
2.2 Registration intention (dichotomous): school setting (ICC adjusted)	6	6272	Risk Ratio (M‐H, Random, 95% CI)	1.34 [1.27, 1.42]

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
8.1 Intention to register	2	284	Mean Difference (IV, Random, 95% CI)	0.73 [0.16, 1.30]
8.2 Verified registration	1	4638	Risk Ratio (M‐H, Random, 95% CI)	0.70 [0.55, 0.90]

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
9.1 Intention to donate	3	1078	Mean Difference (IV, Random, 95% CI)	0.51 [0.27, 0.74]
9.2 Verified registration	1	271574	Risk Ratio (M‐H, Random, 95% CI)	1.37 [1.31, 1.43]

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
10.1 Intention to register	3	1306	Mean Difference (IV, Random, 95% CI)	0.09 [‐0.23, 0.40]
10.2 Accepting donor card	2	896	Risk Ratio (M‐H, Random, 95% CI)	1.12 [0.99, 1.26]

*Study characteristics*
Methods	Study design: cluster‐RCT with a pre/post‐test (two arms) Study duration: not reported Study follow‐up period: not reported
Participants	Country: Spain Setting: Classroom Number: treatment group (109); control group (48) Mean age ± SD (years): 15.36 ± 0.72 (mean age was calculated for the entire sample, not by group) Sex (M/F): Treatment group (56/53); control group (20/28)
Interventions	Intervention group The intervention consisted of 4 sessions. In session 1, students were given a pretest and had a discussion about previous awareness regarding organ donation. In session 2, students viewed the video "Seeing to Donate." In addition, students debated their values and attitudes, and discussed awareness of attitudes in the family setting. In session 3, students talked about the results of the home discussion, and the researcher and transplant coordinator gave an explanation of the donation‐extraction‐transplant process in Malaga. In addition, a young undergraduate on the kidney transplant waiting list gave a testimony. Finally, in session 4, students designed a slogan as a group, and received the post‐test Control group No description given
Outcomes	Primary outcome Intention to donate own organs (measured via self‐completed questionnaire) Intervention group: (91/109) 83.5% stated they would donate their own organs Control group: (27/48) 56.3% stated they would donate their own organs Adverse events were reported Other outcomes Awareness about donation‐extraction‐transplant process (percent of participants reporting having none, low, high, and very high level of information) Intervention group: 0%, 3.4%, 72.5%, 23.9% Control group: 18.7%, 50%, 29.2%, 2.1%n Intention to donate organs from relatives: Intervention group: 77.1% stated they would donate a relative's organs Control group: 50% stated they would donate a relative's organs Family discussion Intervention group: 78.9% stated they had spoken about the subject in the time between pretest and post‐test Control group: 20.8% stated they had spoken about the subject in the time between pre and post‐test
Notes	Funding source: not reported Study author contact: blamen@uma.es (Prof Maria Jose Blanca) Classes were randomly divided into a control or intervention group
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient detail about randomisation scheme
Allocation concealment (selection bias)	Unclear risk	Insufficient detail about allocation method
Blinding of participants and personnel (performance bias) All outcomes	High risk	Insufficient detail about whether there was blinding of participants/personnel. Seems likely that participants may be aware of class allocation and thus, there may be a risk of performance bias
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Self‐reported questionnaire likely to have low risk of detection bias
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Insufficient detail about handling of incomplete outcome data
Selective reporting (reporting bias)	High risk	Important detail re: numerator/denominator/confidence intervals/P values missing
Other bias	Unclear risk	Contamination can be an issue with classroom education and authors did not discuss this issue

*Study characteristics*
Methods	Study design: cluster‐RCT Study duration: not reported Study follow‐up period: not reported
Participants	Country: USA (Chicago, Phoenix, Miami) Setting: "Town halls" (churches in Chicago, universities in Phoenix, local organisations in Miami) Number: not reported; ranged from 15‐59 participants at each town hall Mean age (years) Chicago: intervention group (51.7); control group (47.5) Phoenix: intervention group (32.4); control group (22.0) Miami: intervention group (43.5); control group (56.2) Sex (% female) Chicago: intervention group (64.5%); control group (73.0%) Phoenix: intervention group (64.1%; control group (61.0%) Miami: intervention group (69.4%); control group (78.7%)
Interventions	Two “town halls” were implemented in each city. Donor registration forms were provided to participants following a 1‐hour presentation by an organ donor expert panel (e.g. donor recipient, donor family member, an OPO health educator, and a physician/clinician). Following the presentation and approximately 15 minutes before the completion of the meeting, surveys and donor registration forms were distributed among audience members. Town halls within each of the three cities were randomly assigned to either an intervention (immediacy condition) or control group (non‐immediacy condition) Intervention (immediacy condition) Participants were told to complete the donor registration forms and drop them, along with the survey in a collection box prior to leaving the meeting Control (non‐immediacy condition) Participants were given a self‐addressed stamped envelope before leaving and asked to mail in their donor registration forms on their own time
Outcomes	Primary outcome Completed and submitted an organ donation registration form Intervention group: 42/104 registered Control group: 11/107 registered No adverse events were reported
Notes	Study author contact: Eusebio.Alvaro@cgu.edu Registration rates varied across the cities. In Chicago, Phoenix and Miami saw participants register in the intervention group at a rate of 27%, 67% and 41% respectively. None of the participants from the control group in both Chicago and Phoenix completed and submitted a donor registration form. In Miami, 23.4% of those in the control group mailed in a completed donor registration form
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient detail about randomisation scheme
Allocation concealment (selection bias)	Unclear risk	Insufficient detail about allocation method
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Insufficient detail about blinding however, blinding of personnel unlikely to affect outcome
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Registration in a donor registry is unlikely to be affected by detection bias
Incomplete outcome data (attrition bias) All outcomes	Low risk	Minimal loss to follow up
Selective reporting (reporting bias)	Low risk	Outcome measures reported
Other bias	High risk	Each site could recruit their own participants

*Study characteristics*
Methods	Study design: cluster RCT with a pre/post‐test (two arms) Study duration: June 2008 to March 2009 Study follow‐up period: not reported
Participants	Country: USA Setting: Churches (22 sites) Number: intervention group (622); control group (632) Mean age (years): intervention group (50.30); control group (50.18) Sex (% female): intervention group (70.53%); control group (70.63%)
Interventions	Churches were assigned to either an intervention or control. Researchers provided a 4‐hour long training session to 100 peer leaders from the 22 churches Intervention group Peer‐led motivational discussion on organ donation plus a video viewing. Peer leaders received training on how to complete informed consent documents and administer baseline questionnaires, overview of study design, program components and expectations, basic information about diabetes, hypertension, chronic kidney disease, nutrition. The 32‐minute video "living on through love" featured a local African American donor family, organ recipients, nephrologist, transplant surgeon and pastor. Participants were also provided information on the different religious views on organ donation Control group Received only information on how to complete consent documents, administer baseline questionnaires and overview of study design, program components and expectations. Additionally received content on a fruit and vegetable program
Outcomes	Primary outcome Verified registration in state's donor registry. Outcome was provided by State Organ procurement agency Study was only able to reach 923/1254 (74%) participants at the 12‐month follow‐up period. The intervention group had 622 participants and the control group had 632 participants who completed the baseline questionnaire, where a total of 211 registrations from participating churches were verified Intervention group: 163/622 registered Control group: 48/632 registered Intention to donate (mean score from 1 to 10) among those not registered at post‐test were 5.8/10 in intervention group compared to 5.2/10 in control group (P = 0.38)
Notes	Funding source: Health Resources and Services Administration, Healthcare Systems Bureau, Division of Transplantation Study author contact: Ann M. Andrews (aandrews@nkfm.org) Churches were pair‐matched by average income and size prior to randomisation *Study authors noted that only 192/211 of the registrants completed the baseline questionnaire
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient detail about randomisation scheme
Allocation concealment (selection bias)	Unclear risk	Insufficient detail about allocation method
Blinding of participants and personnel (performance bias) All outcomes	High risk	Insufficient detail about whether there was blinding of participants/personnel. Seems likely that participants may be aware of class allocation and thus, there may be a risk of performance bias
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Verified registration in donor registry not affected by blinding of outcome assessment
Incomplete outcome data (attrition bias) All outcomes	Low risk	26% of baseline participants did not provide follow‐up questionnaire. Authors reported no difference from those that dropped out of the study to those who completed follow‐up
Selective reporting (reporting bias)	Low risk	Outcome measures reported
Other bias	High risk	Baseline groups not equal. For verified registrations, most did not complete a baseline questionnaire

*Study characteristics*
Methods	Study design: quasi‐RCT with a pre/post‐test (2 arms) Study duration: not reported Study follow‐up period: not reported
Participants	Country: USA Setting: Family physician office Number: intervention group (40); control group (125) Mean age: not reported(all participants were 18 years of age or older) Sex: not reported
Interventions	Patients being seen were assigned to one of two intervention groups (every 4th patient was assigned to the experimental group). Patients completed a baseline questionnaire at the time of visit, and then received a pamphlet (the pamphlet answered commonly asked questions regarding organ donation) and an organ donation sticker. After the visit, patients were given the second questionnaire regarding their decision to commit to organ donation, what was their decision, and whether they discussed this choice with family members Intervention group Received informational material + brief word of encouragement from treating physician Control group Received informational material only
Outcomes	Primary outcome Self‐reported commitment to organ donation registration (yes/no). The authors report between‐group comparisons for 165 participants: intervention group (40); control group (125) Intervention group: 12/40 (30%) self‐reported making the decision to donate after the intervention Control group: 53/125 (42%) self‐reported making the decision to donate after the intervention Secondary outcome Knowledge scores regarding organ donation (scores for the knowledge variables were summed for pretest and post‐test, with a total of 10 questions. A significant increase in knowledge regarding organ donation was found between pretest and post‐test (7.9 and 9.2, P < 0.01) No adverse effects were reported
Notes	Funding source: not reported Study author contact: Susan Bidigare (sbidigar@med.wayne.edu) Denominator/numerator for intervention and control group were not reported Every 4th patient assigned to intervention (informational material + brief word of encouragement from treating physician)
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Non‐random component in the sequence generation process ("every 4th patient assigned to intervention")
Allocation concealment (selection bias)	High risk	Physician could potentially foresee allocation assignment
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Insufficient detail about whether there was blinding of participants/personnel
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Self‐reported questionnaire likely to have low risk of detection bias
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Insufficient detail about missing data or lost to follow up
Selective reporting (reporting bias)	High risk	Outcomes of interest not reported completely (proportions only)
Other bias	High risk	Study did not report baseline differences

*Study characteristics*
Methods	Study design: RCT Study duration: not reported Study follow‐up: not reported
Participants	Country: USA Setting: online (Amazon's MTurk) Number: positive affect (261); negative affect (242) statistics regarding age and sex were only provided for the entire cohort (503) Mean age ± SD: 33.59 ± 11.31 years Sex (% female)*: 42%
Interventions	Participants were randomly assigned to either a positive or negative affect condition, involving an autobiographical recall task. Participants were asked to recall a time when they felt positive or negative (the task did not mention any specific emotions). Participants then completed the post‐test questionnaire Positive affect condition Participants were asked to recall a time when they felt particularly positive Negative affect condition Participants were asked to recall a time when they felt particularly negative
Outcomes	Those in the positive affect condition reported significantly higher scores on the general positive affect scale Primaryoutcome Attitudes towards organ donation registration, registration intention Attitudes (measured on 7‐point scale): 4.31 positive affect versus 4.01 negative affect, there was a significant difference between the positive and negative affect conditions in attitudes towards organ donor registration Intention to register (7‐point scale): 3.80 positive affect versus 3.83 negative affect, no significant difference was found between positive and negative affective conditions Secondary outcome Registration behaviour proxy (question: would you like to register as a donor?) Authors reported no significant effect of affect condition on registration behaviour was found. (B = ‐0.14, SE = 0.34, Wald v2 (1) = 0.16, P = 0.690)
Notes	Funding source: grant number R39OT26990 Contact: Danielle Blazek, danielle.blazek@cgu.edu
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient detail about random sequence generation
Allocation concealment (selection bias)	Low risk	Insufficient detail about allocation concealment but study was administered via Amazon mTurk and participants unlikely affected by selection bias
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Online nature of study unlikely to affect performance bias
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Outcomes measured via self‐reported questionnaire
Incomplete outcome data (attrition bias) All outcomes	Low risk	Study states "no cases of missing data were identified"
Selective reporting (reporting bias)	Low risk	All data appear to be fully reported
Other bias	Low risk	No other major biases

*Study characteristics*
Methods	Study design: cluster‐RCT with pre/post‐test (two arms) Study duration: not reported Study follow‐up period: not reported
Participants	Country: USA Setting: classroom Number: intervention group (96); control group (91) Mean age ± SD (years): intervention group (15.9 ± 1.3); control group (16.6 ± 1.4) Sex (% males): intervention group (62.5%); control group (67.0%)
Interventions	All students received a baseline questionnaire and then within two weeks, the classes were assigned to either an experimental or a control group Intervention group A single 40‐minute classroom session moderated by an African American or Asian American representative from a local community health agency. A transplant surgeon delivered current medical information and a 10‐minute video featuring ethnically‐diverse teenagers discussing organ donation and a Q/A period. Completed the second questionnaire AFTER receiving the education session Control group No intervention. Students completed the second questionnaire BEFORE receiving the educational session
Outcomes	Primary outcome Willingness to donate organ Intervention group had 78 participants and control group had 75 participants; 153 pairs of completed questionnaires (completed and responded to opinion question on baseline and second questionnaire completed) Intervention group: 31% (24/78) of experimental participants changed their opinions in a positive direction, 14% (11/78) in a negative direction and 55% (43/78) remained unchanged Control group: 7% (5/75) changed opinions positively, 8% (6/75) negatively and 85% (64/75) were without change OR of 7.14 positive change in willingness to donate (P < 0.0001) Referent = intervention OR of 2.272 moving down the willingness scale (P = 0.065) Referent = intervention Adverse events: more participants in the intervention group changed their attitudes in a negative direction, (14% versus 8%)
Notes	Funding source: National Institute of Allergy and Infectious Disease grant R18AI40674 Study author contact: Margaret D. Allen (mallen@benaroyaresearch.org)
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomisation conducted by a coin toss
Allocation concealment (selection bias)	Unclear risk	Insufficient detail about allocation method
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Participants in both groups aware that they will receive an educational session, thus unlikely that they were aware of group allocation
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Self‐reported questionnaire likely to have low risk of detection bias.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No students were excluded and limited missing data.
Selective reporting (reporting bias)	Low risk	Appropriate outcomes measured
Other bias	High risk	Baseline groups not similar; different in age, and ethnicity (more Europeans in control group).

*Study characteristics*
Methods	Study design: factorial RCT; 2 x 2 between‐subjects factorial design (4 arms; loss/gain x exemplar/statistical message) Study duration: not reported Study follow‐up period: not reported
Participants	Country: Taiwan Setting: classroom Number: 189 college students (authors did not specify how many in each of the 4 groups) Mean age ± SD: 21.6 ± 2.9 years Sex (M/F): 81/108
Interventions	Participants completed a baseline questionnaire on demographic characteristics. After completion, participants were randomly assigned to read 1 of 4 versions of an organ donation promotional message (messages contained in Table 1) Statistical messages emphasised numbers, while exemplar messages depicted an individual's story. Gain‐framed messages conveyed that patients would survive due to organ donation, while loss‐framed messages conveyed that patients would die if organs were not available. Final questionnaire answered after reading of the respective message Group 1 Gain‐statistical message Group 2 Loss‐statistical message Group 3 Gain‐exemplar message Group 4 Loss‐exemplar message
Outcomes	Primary outcome Intention to register as an organ donor, intention to discuss decision with relevant individuals. Both items were rated on a scale 7 point scale (strongly disagree to strongly agree), and the ratings of the 2 items were summed to create an intention scale No significant main effect of gain (4.58 ± 1.00) compared to loss‐framed (4.33 ± 1.19) messages on intention scores Significant main effect of statistical/exemplar messages found (P < 0.05). Participants exposed to exemplar message (4.77 ± 0.89) were significantly more likely to express behavioural intention to become an organ donor, compared to the statistical message (4.15 ± 1.19) Significant interaction between conditions also found. Loss‐exemplar appeal more effective than loss‐statistical appeal (P < 0.01) No adverse effects were reported in this study
Notes	Funding source: financial support provided by the Ministry of Science and Technology of the Republic of China under Project MOST 101‐2410‐H‐003‐045‐MY2 Study author contact: Yu‐Hung Chien (roland.chien@ntnu.edu.tw)
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient detail about randomisation scheme
Allocation concealment (selection bias)	Unclear risk	Insufficient detail about allocation concealment
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Insufficient detail about whether there was blinding of participants/personnel
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Self‐reported questionnaire likely to have low risk of detection bias
Incomplete outcome data (attrition bias) All outcomes	Low risk	Study completed in a single session so unlikely risk of attrition bias
Selective reporting (reporting bias)	Low risk	Outcome measures reported
Other bias	High risk	Did not report baseline differences

*Study characteristics*
Methods	Study design: cluster RCT (3‐arm) Study duration: not reported Study follow‐up period: 6 months
Participants	Country: USA (Western Pennsylvania and Western Virginia) Setting: primary care clinics Sample size Distinct local offices (121) In‐person: 47 offices Web‐based: 33 offices Control: 41 offices A total of 1521 clinic staff were trained, and surveys were returned from 66.4% of staff (1011) In‐person: 442 Web‐based: 369 Control: 200 Patients not previously designated (10,007) In‐person: 6245 Web‐based: 3183 Control: 579 Age (years) Overall: 73.2 In‐person: 18 to 64 (72.2%); 65+ (27.8%) Web‐based: 18 to 64 (74.8%); 65+ (25.2%) Control: 18 to 64 (69.3%); 65+ (30.7%) Sex Overall: 57.7% female In‐person: 57.1% female Web‐based: 58.5% female Control: 61.9% female
Interventions	Intervention included a 1‐hour training session (in‐person or web‐based) regarding organ/tissue donation, in addition to the availability of donor designation forms at check‐in that were given to all patients as they check in. Control consisted of a standard brochure only (no training or donor designation forms) In‐person A trained interventionist delivered a 1‐hour course explaining the organ donation process and implementation of the program in primary care offices. There was an opportunity for interactive discussion and for members of the research team to help front desk staff to set up the donor designation forms Web‐based Materials were mailed to the office with instructions to access the content online. The online content consisted of the same material that were delivered in‐person, but in a web‐based format. The interventionist contacted office managers within 1 week to check compliance with training. A member of the research team dropped off the donor designation forms and other materials Intervention Staff at the primary care offices received a 1‐hour training session regarding organ donation, and were also provided with donor designation forms to give to all patients at check‐in Control Primary care offices received standard organ donation brochures
Outcomes	Primary outcome Actual registration rates as verified by the donor registry The main outcome was the proportion of patients who had not previously been registered as organ donors that completed the donor designation part of the PSL (Patients Save Lives) form Intervention groups: the intervention groups had a higher rate of previously undesignated patients choosing to designate themselves as organ/tissue donors than the control group. The in‐person arm had a slightly higher rate of new donor designations than the web‐based group (8.6% versus 7.1%; P = 0.011) In‐person: 536/6245 (8.6%) Web‐based: 225/3183 (7.1%) Control group: 0/579 (0%) Secondary outcomes Staff self‐report surveys captured staff knowledge and attitudes about organ donation Intervention groups Knowledge: staff in the intervention groups were more informed about organ donation than control. Participants scored 67% in the in‐person group, and 68% in the web‐based group, compared to only 57% correct in the control group (F = 49.46; P < 0.0000) Attitude: More positive attitudes towards organ donation were noted for the in‐person group (4.51), followed by the web‐based group (4.40), followed by the control group (4.28) (F = 13.03; P = 0.00) Control group Knowledge: 57% Attitude: 4.28
Notes	Funding source: Grant No. R39OT29881 from the Health Resources and Services Administration’s Division of Transplantation (HRSA/DoT), U.S. Department of Health and Human Services Study author contact: degen@pitt.edu
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Study authors state that physicians were randomised into 1 of 3 study arms
Allocation concealment (selection bias)	Unclear risk	No information provided regarding allocation concealment
Blinding of participants and personnel (performance bias) All outcomes	High risk	Based on the nature of the intervention, it is unlikely that the primary care physicians would be unaware of their treatment allocation. Thus, high risk of bias
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Primary outcome was donor designation status. Measurement of this outcome is unlikely to be impacted by bias
Incomplete outcome data (attrition bias) All outcomes	Low risk	Organ procurement organisations sent back all donor designation forms to study team. Thus, low risk of attrition bias
Selective reporting (reporting bias)	Low risk	All outcomes appear to be reported
Other bias	Unclear risk	Intervention was a one‐off session, staff data were collected shortly after delivery; 33.6% of staff who were trained did not return the self‐report survey

*Study characteristics*
Methods	Study design: cluster RCT Study duration: 5 hours Study follow‐up period: 1 year
Participants	Country: Belgium Setting: High School Number: 1328; 6 control schools, 6 intervention schools Age: +17 years Sex: not reported
Interventions	Intervention consisted of a young patient's witness, letter of a mother of a young donor, targeted information, explanation of the law and information on how one can register for organ donor
Outcomes	Primary outcome Intention to register Authors reported intention to register as a donor increased to 40% in intervention group, while control group remained steady at 25% (RR 1.98, 95% CI: 1.5 to 2.7)
Notes	Author contacted back in 2013 and they reported that they have not published. Author followed up in 2019
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information (abstract only)
Allocation concealment (selection bias)	Unclear risk	Insufficient information (abstract only)
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Insufficient information (abstract only)
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Self‐reported questionnaire likely to have low risk of detection bias
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Insufficient information (abstract only)
Selective reporting (reporting bias)	High risk	Numerator denominator not reported for intention to register
Other bias	High risk	Only abstract included

*Study characteristics*
Methods	Study design: multi‐arm RCT (3 arms) Study duration: not reported Study follow‐up period: not reported
Participants	Country: Ireland Setting: shopping centre Number: group 1 (113); group 2 (119); group 3 (117) Mean age ± SD (years): group 1 (40.2 ± 17.8); group 2 (42.8 ± 16.8); group 3 (40.6 ± 17.5) Sex (% female): group 1 (46.4%); group 2 (44.5%); group 3 (48.7%)
Interventions	Participants were randomly assigned to 1 of 3 groups based on a computer generation program. All subjects participated in interviews from research staff Group 1 (replication group) Participants completed the questionnaire in its entirety Group 2 (omitting affective attitudes) Participants completed a version of the questionnaire with 16 affective attitude items omitted Group 3 (omitting negatively‐worded affective attitudes) This group completed the questionnaire, but with 12 negatively‐worded affective attitude items omitted
Outcomes	Primary outcome Intention to donate (Ireland does not have a registry, so participants were asked about their intention to sign up to be a donor). Mean intention scores: group 1 (4.43 ± 1.89); group 2 (4.95 ± 1.64); group 3 (4.88 ± 1.81) Group 2 had a statistically significant higher mean intention score than Group 1. Group 3 had a larger mean intention score to Group 1, but did not reach statistical significance Secondary outcome Taking a donor card after the interview Individuals in group 2 were marginally more likely to accept a donor card than Group 1 (OR 1.4, 95% CI 0.94 to 2.07) Group 3 individuals were not more likely to accept a donor card than Group 1 (OR 1.1, 95% CI 0.69 to 1.75)
Notes	Funding source: RSCI Summer Research School (grant to two authors) Study author contact: Sally Doherty (sallydoherty@rcsi.ie) Defined willingness to donate as meeting any of the following four conditions: 1) carrying a signed donor card 2) indicating donation status on drivers license 3) providing information on an organ donation app; and 4) discussing one's wishes with family members
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Participants randomly assigned using a computer generation program
Allocation concealment (selection bias)	High risk	Interviewers were aware of which group the next person they approached was randomised
Blinding of participants and personnel (performance bias) All outcomes	High risk	Single‐blinded study. However, likely that lack of blinding of personnel may affect performance bias given that evaluators interviewed the participants
Blinding of outcome assessment (detection bias) All outcomes	High risk	Single blinded study. However, intention to register as an outcome may be influenced by lack of blinding since participants were interviewed by evaluators
Incomplete outcome data (attrition bias) All outcomes	Low risk	Single session with no loss to follow up
Selective reporting (reporting bias)	Low risk	All outcomes reported
Other bias	Low risk	No other major biases identified

*Study characteristics*
Methods	Study design: RCT (3‐arm) Study duration: study start date: February 2016; primary completion date: December 2017, Study completion date: April 2018 Study follow‐up period: no follow‐up
Participants	Country: international; Ireland, Malaysia, India (countries that do not have an organ donation registry) & UK (does have a register) sample Setting: community; participants were recruited in‐person from community (shopping centres, libraries, university campuses) Sample size: 1007 non‐donors Mean age ± SD: 34.4 ± 18.1 years Gender: 54.0% female
Interventions	Overview: In India, Ireland, and Malaysia, one of three questionnaires were verbally delivered to participants. Interviewers approached potential participants, and delivered the questionnaire face‐face. Researchers filled in the questionnaires for the participants. In the UK, questionnaires were given to participants to be self‐completed in the library, which were then returned to the researchers. After provision of a study information leaflet and consenting to participate, participants provided demographic information and then answered 27 questions about organ donation beliefs. Affective attitudes (ick factor; jinx factor; medical mistrust; perceived benefits; bodily integrity). Anticipated regret (2 items). Theory of planned behaviour (cognitive attitudes; perceived behavioural control; subjective norms; dummy items). Intervention group Omitted affective attitudes: all 16 questions on affective attitudes were deleted, with dummy questions (e.g., about politics) substituted for these deleted questions (as in the INORDAR trial). Omitted negatively‐worded affective attitudes only: omitted 12 negatively‐worded affective attitudes only, which were substituted with the same questions as other intervention group. Control group No‐intervention replication group: completed the entire questionnaire (similar to the anticipated regret group from INORDAR), replicating methods of O’Carroll et al. 2011)
Outcomes	Primary outcome Self‐reported intention to register as a donor: intention to donate, assessed by 2 items on a 7‐point scale (e.g., “I will definitely sign up for organ donation and discuss this with my family in the next few months”) Intervention groups Omitted affective attitudes: 4.30 ± 1.57) (n = 323) Omitted negatively‐worded affective attitudes only: 4.47 ± 1.56 (n = 343) There were no significant group differences seen in intention to donate Control group No‐intervention replication group: 4.44 ± 1.66 (n = 341) Secondary outcomes The secondary outcome (where applicable) was taking a donor card after the interview (study 1; yes/no) Intervention groups Omitted affective attitudes: 51.6% Omitted negatively‐worded affective attitudes only: 48.4% There were no significant group differences seen in those who took a donor card Control group No‐intervention replication group: 46.3%
Notes	Funding source: This research was supported by the RCSI Research Summer School and the RCSI Student Selected Component, who had no role in recruitment, data analysis or interpretation. Study author contact: fdoyle4@rcsi.ie
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Participants were block‐randomised using the ralloc command for Stata 13.0, and Excel sheets with the order of participant recruitment needed was sent to researchers
Allocation concealment (selection bias)	High risk	Group allocation was centrally and pre‐determined, interviewers were aware of group allocation
Blinding of participants and personnel (performance bias) All outcomes	High risk	Study personnel were not blinded to treatment condition, and approached participants themselves and delivered the questionnaire as well. The lack of blinding thus leaves potential for performance bias
Blinding of outcome assessment (detection bias) All outcomes	High risk	Outcomes were all reported on a 7‐point Likert scale, and answers were solicited by interviewers who were not blinded to treatment condition. Thus, there is potential for detection bias
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Outcome data was unavailable for some participants, but no reasoning is provided for this loss‐to‐follow‐up. There is insufficient information to judge risk of bias
Selective reporting (reporting bias)	Low risk	All outcomes appear to be reported
Other bias	Low risk	No other bias identified

*Study characteristics*
Methods	Study design: RCT (6‐arm) Study duration: February to March 2018 Study follow‐up period: no follow‐up
Participants	Country: Japan Setting: Driver’s license centre Sample size: 3224 Mean age ± SD: 44.39 ± 12.74 years Sex: 59.2% male
Interventions	Three investigators randomly distributed leaflets, which included the study questionnaire, before the driver training started at the license renewal centre Intervention consisted of reading a leaflet with different messages that prompted organ donation registration. There were 5 types of frames for the messages: “peer”, “gain”, “loss”, “reciprocity”, and “peer + reciprocity”. The control condition involved a leaflet without a prompt message. On all 6 types of leaflets, the method of registering for organ donation was described on the opposite side Intervention groups Peer: “many people have already expressed their intention to donate their organs” Gain: “your intention could make it possible to save the life of 6 people” Loss: “5 people die every week because enough donors are not available” Reciprocity: “You may also need to receive an organ from other donors" Peer + reciprocity: “many people have already expressed their intention to donate organs. It may be necessary for you to receive organs from other people as well Control group The control leaflet did not contain any prompting messages. It included a general description about organ transplantation.
Outcomes	Primary outcome Self‐reported readiness to register as a donor Intervention groups: 2670 participants had not registered previously Peer: 33/526 Gain: 42/556 Loss: 41/527 Reciprocity: 58/552 Peer + reciprocity: 36/530 In adjusted analysis, reciprocity‐framed was significant predictor for increase in the “immediate decision” response (OR ‐1,596, P = 0.041) compared to control Control group: 36/553
Notes	Funding source: This work was supported in part by Health and Labour Sciences Research Grants from the Japanese Ministry of Health, Labour and Welfare, and the Behavioral Economics Research Center at the Institute of Social and Economic Research of Osaka University. Study author contact: khirai@grappo.jp
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	“Three investigators randomly distributed leaflets, which included the study questionnaire” No further detail provided
Allocation concealment (selection bias)	Unclear risk	“Three investigators randomly distributed leaflets, which included the study questionnaire” No further detail provided
Blinding of participants and personnel (performance bias) All outcomes	High risk	Investigators distributed the leaflets prior to the driver training
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Self‐reported questionnaire unlikely to be affected by lack of outcome assessment blinding
Incomplete outcome data (attrition bias) All outcomes	Low risk	Single intervention, data was complete
Selective reporting (reporting bias)	Low risk	All outcomes appear to be reported
Other bias	Low risk	No other major biases identified

PERMALINK

Interventions for increasing solid organ donor registration

Alvin H Li

Marcus Lo

Jacob E Crawshaw

Alexie J Dunnett

Kyla L Naylor

Amit X Garg

Justin Presseau

Abstract

Background

Objectives

Search methods

Selection criteria

Data collection and analysis

Main results

Authors' conclusions

Plain language summary

Summary of findings

Background

Description of the condition

Description of the intervention

How the intervention might work

Why it is important to do this review

Objectives

Methods

Criteria for considering studies for this review

Types of studies

Types of participants

Inclusion criteria

Exclusion criteria

Types of interventions

Types of outcome measures

Primary outcomes

Secondary outcomes

Search methods for identification of studies

Electronic searches

Searching other resources

Data collection and analysis

Selection of studies

Data extraction and management

Assessment of risk of bias in included studies

Measures of treatment effect

Unit of analysis issues

Dealing with missing data

Assessment of heterogeneity

Assessment of reporting biases

Data synthesis

Subgroup analysis and investigation of heterogeneity

Sensitivity analysis

Summary of findings and assessment of the certainty of the evidence

Results

Description of studies

Results of the search

1.

Included studies

Outcomes measured

Excluded studies

Risk of bias in included studies

2.

3.

Allocation

Random sequence generation

Allocation concealment

Blinding

Performance bias

Detection bias

Incomplete outcome data

Selective reporting

Other potential sources of bias

Effects of interventions

Summary of findings 1. Summary of Findings Table ‐ Interventions for increasing solid organ donation registration (dichotomous outcome).

Summary of findings 2. Summary of Findings Table ‐ Interventions for increasing solid organ donation registration intention (dichotomous outcome).

Summary of findings 3. Summary of Findings Table ‐ Interventions for increasing solid organ donor registration (continuous outcome).

1. Categories of strategies included in the interventions.

Overall effects

1.1. Analysis.

2.1. Analysis.

3.1. Analysis.

School‐based setting (14 studies)

*Study characteristics*
Methods	Study design: factorial and multi‐arm (4 arms) Study duration: not reported Study follow‐up period: 1 month
Participants	Location: Australia Setting: Online (web‐based survey) Number: motivational (42); volitional (36); combined (38); control (61) Mean age ± SD (years): motivational (46.90 ± 14.95); volitional (46.49 ± 16.42); combined (46.19 ± 15.46); control (48.79 ± 13.83) Sex (M/F): motivational (19/23); volitional (15/21); combined (15/23); control (24/37)
Interventions	Each participant was randomly assigned to one of four arms. Both the motivational and volitional interventions were derived from a previous study. Intervention groups Motivational: designed to strengthen people's intentions to communicate by encouraging supportive attitudes and norms Volitional: participants created both action and coping plans to strengthen behaviour. For action planning, participants filled in the blanks in a statement for registering and discussing which specified when, where and how communication of their donation wishes would occur. For coping planning, participants listed three obstacles that may interfere with their plans and suggested three solutions they could use to successfully overcome the identified barriers Combined: both the motivational and volitional arms Control group No description given
Outcomes	Primary outcome Self‐reported registration in the Australian Organ Donor Register and self‐reported discussion of organ donation preference with relevant individuals Self‐reported registration behaviour Motivational: 5/35 registered (14.3%) Volitional: 7/28 registered (25.0%) Combined: 13/31 registered (41.9%) Control: 7/45 registered (15.6%) Self‐reported intention to register also measured (143): not all groups compared Motivational: 5.08 ± 1.84 (67) Volitional: 4.27 ± 1.94 (76) Discussing organ donation preference (88 discussed in total) Motivational: 6/19 (31.6%) discussed Volitional: 4/20 (20%) discussed Combined: 6/18 (33.3%) discussed Control: 11/31 (35.5%) discussed No adverse effects were reported in this study
Notes	Funding source: Queensland University of Technology, Vice Chancellor's Postdoctoral Research Fellowship Support Grant Study author contact: Melissa Hyde (melissa.hyde@griffith.edu.au)
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomisation conducted by a computer generated sequence
Allocation concealment (selection bias)	Low risk	Used computer to allocate
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Insufficient detail about blinding of participants and personnel
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Self‐reported questionnaire likely low risk of detection bias
Incomplete outcome data (attrition bias) All outcomes	High risk	Did not provide demographic information on those who only completed baseline questionnaire (loss to follow‐up) and they had different scores on attitudes and moral norm towards organ donation
Selective reporting (reporting bias)	High risk	All outcomes reported appropriately
Other bias	Low risk	No other biases

*Study characteristics*
Methods	Study design: multi‐arm RCT (4 arms) Study duration: April to October 2012 Study follow‐up period: registry checked 6 months later
Participants	Country: Scotland Setting: mailing campaign Number: NQC (2330); QC (2257); TPB (2313); AR (2308) Mean age ± SD (years): NQC (41.28 ± 11.70); QC (40.81 ± 11.65); TPB (41.32 ± 11.95); AR (40.65 ± 11.83) Sex (% male): NQC (43.79%); QC (44.53%); TPB (43.47%); AR (43.35%)
Interventions	Participants were randomly assigned to one of four arms, using simple randomisation in a 1:1:1:1 ratio. A market research company did the randomisation sequence and participant enrolment/assignment, to which all participants were blind to the experimental arm No questionnaire control (NQC) Participants completed a survey collecting their demographic information, whether or not they were a registered donor, if they knew of anyone who had received an organ transplant, if they knew anyone who had donated an organ, if they knew anyone who needed an organ, whether or not they had ever donated an organ and whether or not they had ever donated blood Questionnaire control (QC) Participants completed the same questionnaire that was given to the NQC group, with the addition of 16 extra items. Additional items measured their non‐cognitive affective attitudes towards organ donation (i.e. bodily integrity, medical mistrust, 'ick' factor, jinx, perceived benefits). All items were rated on a 7‐point scale from 1 "strongly disagree" to 7 "strongly agree." Participants also rated their intention to register as an organ donor on a 2‐item scale. Nine of the survey items were filler items to ensure that the number of items in the QC arm were identical to the TPB/AR arms Theory of planned behaviour questionnaire (TPB) Questionnaire had the same affective and intention items as the QC questionnaire, plus an additional 7 items. Additional items measured attitude, subjective norm and perceived control. Two additional filler items were included to ensure the total number of items was equal to that of the AR arm Anticipated regret questionnaire (AR) Questionnaire contained the same affective, intention and TPB items as the TPB arm, plus an additional 2 items that measured the extent to which the participant would anticipate regret for not registering as an organ donor
Outcomes	Primary outcome Verified registration of participants in the UK organ donor registry (a total of 497/9208 (5.4%) participants registered as a verified organ donor) NQC: 149/2330 participants registered QC: 119/2257 participants registered TPB: 125/2313 participants registered AR: 104/2308 participants registered Participants in the NQC group were more likely than the AR group to register in the UK organ donor registry (P = 0.042) No adverse events were reported
Notes	Funding source: grant from The Scottish Government Chief Scientist's Office (Ref. CZH/4/686) Study author contact: Ronan E. O'Carroll (reo1@stir.ac.uk)
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Market research company performed the randomisation using simple randomisation
Allocation concealment (selection bias)	Low risk	Mail‐out study unlikely to be affected by lack of allocation concealment
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Participants were blinded to the experimental arm
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Unlikely that donor registration in the registry is affected by lack of blinding of outcome assessment
Incomplete outcome data (attrition bias) All outcomes	Low risk	Single session
Selective reporting (reporting bias)	Low risk	All outcomes appear to be reported
Other bias	Low risk	No other major biases identified

*Study characteristics*
Methods	Study design: RCT Study duration: 25 August 2014 to 3 October 2014 Study follow‐up period: 39 days
Participants	Country: Japan Setting: nursing university Number: intervention group (102); control group (101) Median age, IQR (years): intervention group (19, 19 to 20); control group (20, 19 to 20) Sex (% female): intervention group (89.2%); control group (89.1%)
Interventions	Intervention group Participants received a lecture and participated in a small group discussion. The lecture was provided by 2 lecturers: a transplant nephrologist and a kidney transplant recipient. The lectures discussed end‐stage kidney disease, provided an overview of the organ donation system in Japan, and personal experiences (from the transplant recipient) on dialysis therapy and donor kidney transplantation. Participants received an information booklet ("The Gift of Life" at the end, containing a donor card Control group Participants received 3 information booklets, one of which was the same as the intervention group's ("The Gift of Life"). The other two booklets were "Current Status of Transplantation in Japan" and "Kidney Failure: Treatment Options and Practice"
Outcomes	Primary outcome Self‐reported organ donor designation (any of the following: Internet registration, donor card, driver's license, health insurance card). (203/205 students completed the final questionnaire (n=2 excluded from intervention group for absenteeism)) Intervention group: 7/102 (6.9%; Proportion Ratio: 6.93, 95% CI 0.87 to 55.32; P = 0.07) provided consent for organ donation Control group: 1/101 (1.0%) provided consent for organ donation Secondary outcome Measured the proportion of students who (i) obtained approval of family to the student's consent to organ donation, (ii) expressed willingness to provide consent for donation, (iii) expressed willingness to donate organs after brain death, (iv) expressed willingness to donate organs after circulatory death, (v) expressed willingness to approve organ removal from a deceased family member with donor designation, (vi) expressed willingness to approve organ removal from deceased family member with unknown donation status, (vii) discussed deceased organ donation with family, (viii) whose family members provided consent for organ donation Expressed willingness to provide consent for donation Intervention group: 56/102 (54.9%) Control group: 40/101 (39.6%) No adverse events were reported
Notes	Funding source: Yukiko Ishibashi Foundation Study author contact: Professor Shunichi Fukuhara (fukuhara.shunichi.6m@kyoto‐u.ac.jp) Participants were randomly assigned to intervention or control group, in a 1:1 ratio, using computer‐generated random numbers. Non‐blinded. Authors provided additional details of protocol
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomisation conducted by a computer generated sequence
Allocation concealment (selection bias)	Low risk	Allocation conducted by an independent person
Blinding of participants and personnel (performance bias) All outcomes	High risk	Likely that participants aware which group they were assigned to which may have caused them to respond accordingly
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Self‐reported questionnaire likely to have low risk of detection bias
Incomplete outcome data (attrition bias) All outcomes	Low risk	Loss to follow up minimal
Selective reporting (reporting bias)	Low risk	All outcome measures reported
Other bias	High risk	Contamination occurred in 52.0% of the intervention group and 42.6% in the control group

*Study characteristics*
Methods	Study design: pseudo‐RCT Duration of study: not reported Duration of follow‐up: not reported
Participants	Country: Scotland Setting: Shopping mall Number: 138 total, 91 non‐donors Age group (1‐5): 3.7 (1.8) for non‐donors Sex (M/F): 39/52
Interventions	Intervention group Anticipated Regret (AR): participants completed the same questionnaire as above, with the addition of two extra questions assessing anticipated regret: "If I didn't register as an organ donor and someone I cared about died that could have been saved, I would feel regret" and "If I don't register as an organ donor I will later wish that I had." Control group Participants completed a questionnaire assessing five items regarding their attitudes towards organ donation (i.e. bodily integrity, medical mistrust, 'ick' factor, jinx and perceived benefit). They also completed additional questions related to cognitive‐rational factors (three questions to get an overall sense of the participants' attitudes towards the idea of organ donation, five questions to assess their knowledge of organ donation and two questions to measure subjective norm)
Outcomes	Primary outcome Participants intention to become a registered organ donor (measured on a scale from 1 "strongly disagree" to 7 "strongly agree") Intervention (AR): mean intention score: 5.5 (SE 0.28) (SD 1.86) (44) Control group: mean intention score: 4.4 (SE 0.27) (SD 1.85) (47) The mean intention score for the AR condition was significantly higher compared to that of the control condition (P = 0.008)
Notes	Study author contact: Ronan E. O’Carroll (reo1@stir.ac.uk)
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Pseudo‐randomisation with equal number of control and experimental condition
Allocation concealment (selection bias)	Unclear risk	Insufficient detail about allocation concealment
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Unlikely that lack of blinding of participant and personnel would affect performance bias
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Self‐reported questionnaire unlikely to be affected by donor registration status
Incomplete outcome data (attrition bias) All outcomes	Low risk	Single session intervention with no loss to follow up
Selective reporting (reporting bias)	Low risk	All outcomes appear to be reported
Other bias	Low risk	No other major biases identified

*Study characteristics*
Methods	Study design: factorial RCT Study duration: not reported Study follow‐up period: not reported
Participants	Location: UK Setting: online or in‐person (at university campus or local workplaces) Number: intervention group (71); control group (69); face‐to‐face setting (83); online setting (57) Age: intervention group (predominantly 18‐24 years; 40.8%); control group (predominantly 18‐24 years; 29.0%); face‐to‐face setting (predominantly 18‐24 years; 37.3%); online setting (predominantly 18‐24 years; 31.6%) Sex (% female): intervention group (52.1%); control group (62.3%); face‐face setting (56.6%); online setting (57.9%)
Interventions	Participants who were indicated as non‐donors were randomly assigned to either a reciprocity prime or control condition using an online randomization tool. Intervention group Reciprocity prime: participants completed a questionnaire beginning with a priming question, followed by two questions regarding their intention to register as an organ donor. The reciprocity prime was based on marketing materials used by the UK NHS Blood and Transplant's organ donation campaign. Participants were required to respond to the question "I would accept an organ from a deceased donor in order to save my own life," evaluated on a 7‐point Likert scale (from "strongly disagree" to "strongly agree") Control group Participants completed the same questionnaire as the intervention (reciprocity prime) group, but with a neutral 'filler' statement
Outcomes	Primary outcome Participants organ donation registration intention score (evaluated by two questions on a 7‐point Likert scale (i.e. "I strongly intend to donate my organs in the future," "I will definitely donate my organs when I die")). These two questions were averaged to produce one overall intention score (i.e. mean intention score) Prime versus control condition: prime participants scored significantly higher on intention compared to that of the control group Prime condition: 5.64 ± 1.15 (71) Control condition: 4.96 ± 1.44 (69) Face‐to‐face prime condition: 5.54 ± 1.2 (47) Face‐to‐face control condition: 4.85 ± 1.49) (36) Online prime condition: 5.83 ± 1.05 (24) Online control condition: 5.08 ± 1.40 (33) No adverse events were reported
Notes	Funding source: not reported Study author contact: Ronan E. O'Carroll (reo1@stir.ac.uk) Participants were non‐donors
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Online randomisation tool
Allocation concealment (selection bias)	Unclear risk	Insufficient detail about allocation concealment
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Participants were blinded due to nature of intervention
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Outcome assessors were blinded due to nature of intervention
Incomplete outcome data (attrition bias) All outcomes	Low risk	Unclear why the full sample of subjects were not included (518 recruited, but only 511 subjects included in analysis of organ donation intention and 509 included in analysis of behavioural proxy for organ donation registration)
Selective reporting (reporting bias)	Low risk	No reporting bias identified
Other bias	Low risk	No other bias identified

*Study characteristics*
Methods	Study design: clustered RCT with pre/post‐test (two arms) Study duration: not reported Study follow‐up period: 1 year
Participants	Country: USA Setting: Churches (9 sites) Number: intervention group (175); control group (162) Mean age (years): intervention group (49.5); control group (52.5) Sex (% female): intervention (79.4%); control (76.3%)
Interventions	Churches were randomly assigned to either an experimental or control intervention Intervention group Received the Project ACTS intervention package, which consisted of a culturally‐sensitive video, educational pamphlet, donor card, a National Donor Sabbath pendant and other items embossed with the project brand. The video was hosted by a gospel singing group and featured testimonials from individual and family about the organ donation process. The Project ACTS educational pamphlet contained statistics on African Americans waiting list and information on the allocation system Control group Received standard pamphlets on organ donation with a donor card that is available to all consumers
Outcomes	Data was collected at baseline and 1‐year follow‐up. Of 425 participants, 337 (79.3%) completed the follow‐up survey Primary outcome Self‐reported willingness to identify as an organ donor on driver's license Intervention group: 46.9% (82/175) Control group: 48.8% 79/162) Self‐reported willingness to carrying a donor card Intervention group: 24.0% (42/175) Control group: 24.7% (40/162) Study reported no significant differences between experimental and control group No adverse events were reported
Notes	Funding source: National Institute of Diabetes and Digestive and Kidney Diseases (grant #5 R01 DK62617‐05) Study author contact: Kimberly Arriola (kjacoba@sph.emory.edu) Intervention participants were more likely than control participants to review a donation‐related video (56.6% versus 23.6%; chi² P < 0.001) and written materials (69.1% versus 50.9%; chi² P < 0.001)
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient detail about random sequence generation
Allocation concealment (selection bias)	Unclear risk	Insufficient detail about allocation concealment
Blinding of participants and personnel (performance bias) All outcomes	High risk	Likely that participants aware which group they were assigned to which caused them to respond accordingly
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Donor registration likely to have low risk of detection bias
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Although dropout was high (21.5% intervention, 19.8% control), authors addressed that those lost to follow up had similar characteristics to those who completed the second questionnaire. Authors did not provide any additional information
Selective reporting (reporting bias)	Low risk	All outcome measures reported appropriately
Other bias	High risk	Different baseline characteristics among intervention and control. Groups were different in age, educational attainment and income. Authors did not address issue of contamination

*Study characteristics*
Methods	Study design: factorial cluster‐RCT with a pre/post‐test (4 arms) Study duration: April 2009 to February 2011 Study follow‐up period: 1 year (April 2010 to February 2011)
Participants	Country: USA Setting: group setting or at home Number: revised intervention (283); original intervention (302); group setting (288); take‐home setting (297) Mean age (years): revised intervention (46.2); original intervention (46.3); group setting (44.9); take‐home setting (47.6) Sex (% female): revised intervention (70.7%); original intervention (67.5%); group setting (70.1%); take‐home setting (68.0%)
Interventions	Eight focus groups with 5 to 10 individuals (n=59) informed the revision of Project ACTS II materials. Nineteen outreach workers (15 female; 4 male) participated in the intervention delivery. Outreach workers attended one‐on‐one training that described project, study protocol, how to recruit participants, and how to facilitate group discussion. Workers tasked with recruiting up to 32 individuals, and facilitated group discussion Group 1 Revised intervention/group setting: viewed the Project ACTS II DVD and educational booklet in a group setting, followed by group discussion Group 2 Revised intervention/take home: viewed an unrelated DVD (social determinants of health) in a group setting, followed by group discussion, and took Project ACTS II materials home Group 3 Original intervention/group setting: viewed the Project ACTS I DVD and booklet in group setting, followed by group discussion Group 4 Original intervention/take home: viewed an unrelated DVD in group setting, followed by group discussion, and took Project ACTS I intervention materials home
Outcomes	Primary outcome Expression of donation wishes, which was a sum of three behaviours (driver's license, donor card, discussing with family about one's wishes) (scores ranged 3 ‐ 15, higher scores indicate greater willingness to donate) Authors able to reach 509/585 (87%) of participants at the 1‐year follow‐up period Intervention package: no significant effect of condition on expression of donation wishes Setting: significant effect of condition, where participants in the group condition had a larger increase in expression of donation wishes from baseline to follow‐up (baseline = 7.6, follow‐up = 8.9) compared to take home condition (baseline = 7.6, follow‐up = 8.1) No adverse effects were reported in this study
Notes	Funding source: National Institute of Diabetes and Digestive and Kidney Diseases (Grant #5R01DK079713‐05) Study author contact: Kimberly Arriola (kjacoba@sph.emory.edu)
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Used an online randomisation tool
Allocation concealment (selection bias)	High risk	Outreach workers were aware of group allocation
Blinding of participants and personnel (performance bias) All outcomes	High risk	Outreach workers were not blinded and thus, high risk of performance bias
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Self‐reported questionnaire likely low risk of detection bias
Incomplete outcome data (attrition bias) All outcomes	High risk	Those loss to follow‐up had significantly different characteristics than those who completed the study
Selective reporting (reporting bias)	High risk	Did not report mean score of donation intention for donation intention outcome
Other bias	High risk	Did not address issue of contamination by outreach worker

*Study characteristics*
Methods	Study design: multi‐arm RCT Study duration: December 2010 to June 2011 Study follow‐up period: not reported
Participants	Country: USA Setting: direct‐mail campaign Number: letter (42,789); brochure (46,624), letter + brochure (43,001) Mean age: not reported but mail was sent to 18 year olds Sex: not reported
Interventions	Direct‐mail marking strategy. Participants were assigned to one of three arms Letter only from the Secretary of State (SoS) Addressed to individual by first name, encouraged residents to become an organ and tissue donor, stated facts and statistics. The letter concluded by telling residents that joining the registry takes 30 seconds and registration can occur via Internet, phone or returning the attached card Brochure only from the SoS Brochure was informed by multi‐ethnic focus groups. The front featured transplant recipients and facts about organ donation were presented along with a narrative about a family who experienced both recipient and donation side. The brochure described steps to join the organ and tissue donor registry and contained a registration form Combined Letter and Brochure Receiving both the letter and the brochure from the SoS
Outcomes	Primary outcome Registration in Illinois' First‐Person Consent Registry (to track registrations in the registry, each condition contained a 4‐digit code that participants were told to enter when joining) New registrations: 6908 Letter only from the Secretary of State (SoS): 2668/ 42789 (6.2%) (significantly higher compared to brochure only (P < 0.001); no difference compared to combined SoS letter and brochure (P > 0.05) Brochure only from the SoS: 1534/46624 (3.3%) Combined Letter and Brochure: 2706/43001 (6.3%) (P < 0.001 compared to brochure only)
Notes	Funding source: Health Resources and Services Administration's Division of Transplantation grant #R39OT15493‐02 Study author contact: Brian L. Quick (bquick@illinois.edu) Total cost for project was $56 686 Production and mailing cost/cost per registration Letter only: $0.38 Brochure only: $0.41 Combined: $0.43
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient detail about random sequence generation
Allocation concealment (selection bias)	Unclear risk	Insufficient detail about allocation concealment
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Insufficient detail about blinding but participants receiving mail‐outs are likely to have low risk of being aware which group they were assigned to
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Donor registration likely to have low risk of detection bias
Incomplete outcome data (attrition bias) All outcomes	Low risk	Single intervention and those who were excluded were those who had undeliverable mail
Selective reporting (reporting bias)	Low risk	All outcome measures reported appropriately
Other bias	Low risk	No other bias identified

*Study characteristics*
Methods	Study design: clustered‐RCT based upon 1 month post‐intervention (3 arms) Randomisation occurred at the level of the worksite Study duration: not reported Study follow‐up period: 1 month
Participants	Country: USA Setting: worksites (40) through corporations (12) Number: basic (254); enhanced (288); control (213) Mean age: basic (40.9 years); enhanced (41.0 years); control (41.3 years) Sex (% female): basic (77.8%); enhanced (77.4%); control (73.6%)
Interventions	Participants were assigned to one of three arms. All interventions were presented during a 1‐hr "lunch‐and‐learn" program Basic educational Development of intervention was based on the Transtheoretical Model and was a factual presentation designed to raise the worker's awareness of the value of and need for organ donation. The intervention introduced the workers to a trained transplant recipient and a family member of a deceased organ donor and each provided a testimonial. Finally, workers were taught what steps to take to become an organ donor Enhanced educational intervention Basic educational intervention and advice and encouragement for participants to persuade family members to register for organ donation and informing other family members about their choices. This advice included presenting facts about the need/value of donation, sharing testimonials heard in the program, and outlining one's own personal view of the benefits Control group Participants were provided brochures on a range of health‐related topics from diabetes and kidney disease to organ donation. A heath educators facilitated the session
Outcomes	Primary outcome Changes in intention to donate (signed donor card), communication with family regarding organ donation intention, change in family member's intention to be donors (signed donor card). Basic educational: 110/172 registered (64%); rate of change: 29%, P < 0.001 Enhanced educational intervention: 122/179 (68%); rate of change: 31%, P = 0.002 Control group: 81/137 (59%); rate of change, 17%, P = 0.454 Secondary outcome Self‐reported proportion of family members signed donor card. Basic educational: 115/172 (67%); 9% to 17%, P < 0.001 Enhanced educational intervention: 118/179 (66%); 10% to 17%, P < 0.001 Control group: 86/137 (63%); 10% to 14%, P = 0.016 No adverse events were reported in the article
Notes	Funding source: Health Resources and Services Administration, Office of Special Programs, Division of Transplantation, grant # 1‐H39‐OT‐00086‐01 Study author contact: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient detail about random sequence generation
Allocation concealment (selection bias)	Unclear risk	Insufficient detail about allocation concealment
Blinding of participants and personnel (performance bias) All outcomes	High risk	Likely that participants aware which group they were assigned to which caused them to respond accordingly
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Self‐reported questionnaire likely to have low risk of detection bias
Incomplete outcome data (attrition bias) All outcomes	High risk	High loss to follow up (34%). Differences in demographics of those loss to follow up
Selective reporting (reporting bias)	Low risk	All outcome measures reported appropriately
Other bias	Low risk	No major biases identified. However, a proportion of participants reported having signed donor card at baseline but subsequently in follow‐up questionnaire did not have signed donor card which should not have been possible

*Study characteristics*
Methods	Study design: RCT with pre/post‐test (2arms) Study duration: not reported Study follow‐up period: 1 week
Participants	Country: Netherlands Setting: classroom Number: intervention group (125); control group (117) statistics regarding age and sex were only provided for the entire cohort Mean age: 15.4 years Sex(% female): 51%
Interventions	Baseline questionnaire was assigned before the intervention. Participants received the follow‐up questionnaire one week post‐intervention Intervention group Students in the education group were simply invited to practice filling in an invalid but realistic registration form Control group No intervention, standard classroom activities
Outcomes	Primary outcome Intention to fill out the donor registration form Mean scores (standard deviation) for intention to donate (range from ‐3 to +3, fully disagree to fully agree). Question asked was: "Do you intend to fill‐in and return the registration form when you reach the age of 18 years?") The authors reported that the intervention was not significantly associated with registering as a potential deceased organ and tissue donor (OR 1.47; 95% CI 0.67 to 3.25) Intervention group: mean score increased from 0.90 (1.82) to 1.40 (1.59) Control group: mean score increased from 1.00 (1.77) to 1.10 (1.67)
Notes	Funding source: Dutch Kidney Foundation, the Dutch Ministry of Health, CZ Health Insurances and NIGZ/SDV Study author contact: Astrid Reubsaet (a.reubsaet@gvo.unimaas.nl) Primary outcome measure was intention to fill out the form rather than actually registering a deceased organ donor
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient detail about random sequence generation
Allocation concealment (selection bias)	Unclear risk	Insufficient detail about method of allocation concealment
Blinding of participants and personnel (performance bias) All outcomes	High risk	Insufficient detail about blinding. However, it is likely that participants are aware of group allocation and thus, high risk of performance bias
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Self‐reported questionnaire likely low risk of detection bias
Incomplete outcome data (attrition bias) All outcomes	Low risk	Single session likely to have minimal loss to follow up
Selective reporting (reporting bias)	Low risk	All outcomes appear to be reported
Other bias	Low risk	No other major identified biases