4.

Informed consent document developed with input from a consumer group compared with investigator‐developed consent document for Gulf War veterans' illness (Guarino 2006).
Patient or population: Patients with Gulf War veterans' illness Settings: Clinical research at 20 US medical centers Intervention: Consumer‐developed consent document Comparison: Investigator‐developed consent document
Outcomes	Illustrative comparative risks* (95% CI)		No of Participants (studies)	Quality of the evidence (GRADE)	Comments
	Assumed risk	Corresponding risk
	Investigator‐developed consent document	Consumer‐developed consent document
Understanding (consumer influence on healthcare outcomes) Informed Consent Questionnaire‐4. Scale from: 0 to 1. (Follow‐up: 12 months)	The mean understanding in the control groups was 0.728	The mean understanding in the intervention groups was 0.006 higher (0.029 lower to 0.04 higher)	1092 (1)	++OO low§#	Based on this trial there is low quality evidence that consumer consultation in the development of consent documents may have little if any impact on participant’s self‐reported understanding of the trial described in the consent document.
Satisfaction (consumer satisfaction resulting from consumer involvement)			1092 (1)	++OO low§#	Based on this trial there is low quality evidence that consumer consultation in the development of consent documents may have little if any impact on satisfaction with study participation.
Adherence (participation rates of consumers)			1092 (1)	++OO low§#	Based on this trial there is low quality evidence that consumer consultation in the development of consent documents may have little if any impact on adherence to the protocol.
Refusal to participate (participation rates of consumers)			1092 (1)	++OO low§#	Based on this trial there is low quality evidence that consumer consultation in the development of consent documents may have little if any impact on refusal to participate.
*The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (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
GRADE Working Group grades of evidence High quality: Further research is very unlikely to change our confidence in the estimate of effect (++++) Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate (+++O) Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate (++OO) Very low quality: We are very uncertain about the estimate (+OOO)

§ Cluster randomized trial. Unclear allocation concealment and blinding. Drop out less than 20%, however only 71% of the participants completed primary outcome measure at all four visits.

# Not validated questionnaire prior to the trial. Only one trial with 1092 participants.