Establishing the clinical and cost effectiveness of interventions in healthcare largely depends on good quality randomised controlled trials (RCTs). One element of quality in RCTs is the recruitment of sufficient participants to test a priori hypotheses with statistical confidence and to minimise bias.1 However, many RCTs fail to meet their recruitment targets.2
One strategy to increase recruitment to trials is to pay healthcare professionals to recruit subjects either by providing financial incentives or by reimbursing excess costs incurred. Many pharmaceutical companies provide inducements but this is not common practice in publicly funded research programmes. Such programmes need to have confidence that payments are worthwhile. We did a systematic review, therefore, to synthesise the evidence on the effectiveness of payment to healthcare professionals for patient recruitment to trials.
Methods and results
We searched electronic databases (Cochrane Library, Medline, Embase, CINAHL, PsycINFO, Science Citation Index/Social Science Citation Index, Current Controlled Trials, ClinicalTrials.gov, Health Management Information Consortium, National Research Register) from inception to July 2004 for published English language studies of any payment or reimbursement to any healthcare professional recruiting patients to trials with reported recruitment rates. We also searched bibliographies and grey literature. Two independent investigators assessed inclusion criteria, data extraction, and quality using standard systematic review methodology. Quality assessment used the DuRant tool.
The evidence is very limited in quantity and quality and is inconclusive. No controlled trials comparing recruitment rates achieved with and without financial incentives were identified. Three cross-sectional surveys,3-5 within the context of experimental studies, were identified which considered recruitment rates and the attitudes and characteristics of clinicians in relation to some financial incentive or reimbursement (table).
Table 1.
Studies of payment to healthcare professionals for patient recruitment to trials
| Study | Payment | Results |
|---|---|---|
| De Wit, 2001, Netherlands3 Survey in cohort/RCT in primary care | $25 (£15; €21) per patient recruited to cohort study | Financial incentive important for participation: 15% respondents |
| $70 per patient recruited to RCT; incentive paid to family practitioner | Univariate analysis (number recruited to study and financial incentive): Odds ratio cohort study: 1.2 (95% CI 0.4 to 4.1) Odds ratio RCT: 2.0 (0.6 to 6.4) | |
| Pearl, 2003, New Zealand4 Survey after RCT in primary care | $NZ150 (£61; $104; €89) per patient recruited to RCT; financial reimbursement paid to general practitioners | Agreed or strongly agreed financial incentives should be paid: 85% referring GPs |
| Multivariate analysis showed various strategies aid recruitment including financial incentive, which might be enhanced by closer collaboration between GPs and researchers | ||
| Hjorth, 1996 Sweden, Norway, Denmark5 Survey after RCT in hospital setting | $150 per patient recruited up to $450 for follow-up > 18 months; reimbursement paid to clinics | Financial incentive very great or great importance: 14/93 respondents Reimbursement considered adequate: 42/92 respondents Most important factor for recruitment: scientific aim of the study |
None set out to test a hypothesis; all relied on finding associations between characteristics of the practice or clinician and patient recruitment. Other methodological limitations included lack of control groups, self selection of respondents, and inadequate data analysis.
One primary care study reported no relation between incentive driven motivation and number of patients recruited3; the other primary care study4 did not report a correlation between financial reimbursement and recruitment rates but concluded from multivariate analysis that patient recruitment by general practitioners may be aided by a range of strategies, including financial incentives. The hospital based study reported that payment to the participating clinics was considered to be of only minor importance for both participation in trials and for recruiting patients.5
Comment
The limited evidence is surprising when considering the extensive use of payment to healthcare professionals to recruit patients to trials. Although we may have missed some studies it is unlikely that we will have missed rigorous experimental studies designed specifically to investigate financial incentives for recruitment of patients to trials. It may be that such studies are considered unnecessary, either because of extrapolation from the effects of incentives in other areas of healthcare or research (for example, to achieve high immunisation uptake or increase postal survey response rates), or because the success of incentives is self evident. It is unlikely that companies would invest in financial incentives for no return. That such a widespread practice has not undergone experimental evaluation is interesting for three main reasons, however. Firstly, there are important associated ethical issues concerning potential conflicts of interest, disclosure to patients, and implications for informed consent procedures and for the doctor-patient relationship. Secondly, it would be easy to randomise the payment of incentives in a multicentre RCT. Thirdly, there are considerable resource implications associated with research participation. Rigorous evidence from well conducted studies is needed to inform recruitment strategies before publicly funded research programmes can consider the use of financial incentives.
What is already known on this topic
Many randomised controlled trials fail to recruit their target number of participants, which has implications for the validity of their findings
Privately funded research often provides financial incentives to increase patient recruitment, but this is less common in publicly funded research
What this study adds
Evidence on the effectiveness of payment to healthcare professionals for recruiting patients to trials is lacking; funding bodies must consider whether to extrapolate from the evidence of effectiveness of financial incentives in other areas or to undertake new work
Contributiors: JB developed the protocol, helped to develop the search strategy, assessed studies for inclusion, extracted data from and quality assessed included studies, synthesised evidence, and drafted the report. JP developed the protocol, developed the search strategy, assessed studies for inclusion, extracted data from and quality assessed included studies, and edited the draft report. JP is guarantor.
Funding: NHS Health Technology Assessment Programme. These views do not necessarily reflect those of the Department of Health.
Competing interests: None declared.
Ethical approval: Not needed.
References
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