Original articles
Barriers to Participation in Randomised Controlled Trials: A Systematic Review

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Abstract

Method: A systematic review of three bibliographic databases from 1986 to 1996 identified 78 papers reporting barriers to recruitment of clinicians and patients to randomised controlled trials. Results: Clinician barriers included: time constraints, lack of staff and training, worry about the impact on the doctor-patient relationship, concern for patients, loss of professional autonomy, difficulty with the consent procedure, lack of rewards and recognition, and an insufficiently interesting question. Patient barriers included: additional demands of the trial, patient preferences, worry caused by uncertainty, and concerns about information and consent. Conclusions: To overcome barriers to clinician recruitment, the trial should address an important research question and the protocol and data collection should be as straightforward as possible. The demands on clinicians and patients should be kept to a minimum. Dedicated research staff may be required to support clinical staff and patients. The recruitment aspects of a randomised controlled trial should be carefully planned and piloted. Further work is needed to quantify the extent of problems associated with clinician and patient participation, and proper evaluation is required of strategies to overcome barriers.

Introduction

The randomised controlled trial (RCT) is widely accepted as the most powerful research method for minimising bias when evaluating health technologies. However, delays and problems with recruitment of clinicians and patient participants continue to have a major impact on costs and workload of trials 1, 2, and on their subsequent value. The scale of the problem is not well documented, but a survey of recruitment amongst a cohort of 41 randomised controlled trials in the USA found that 34% recruited less than 75% of their planned sample [3]. The effect of reducing the sample size is to reduce the statistical power of the study, and is one of the main reasons for abandoning trials early 2, 4, 5, 6.

Previous reviews of barriers to recruitment have taken a traditional approach, rather than using a systematic methodology 1, 2, in which the selection, evaluation and inclusion criteria are not explicitly pre-defined. For this reason, such reviews may be biased. We report a systematic literature review of barriers to clinician and patient participation in randomised trials, and make recommendations for improving the conduct of trials based on the findings.

Section snippets

Method

An initial systematic search of Medline, Embase, and CINAHL for the period 1986 to 1996 identified 9732 references of possible relevance to problems associated with the design, conduct, analysis or costs of a trial: of these, 265 papers identified clinician participation or patient participation as being an important issue. From this sub-set, all primary research papers were selected which reported findings relating to problems with recruitment of clinicians or patients to clinical trials: only

Results

Brief descriptions of all the reports included in the review are presented in Table 1.

Discussion

Our review took a systematic approach designed to be less selective and therefore less biased than other less rigorous approaches [85]. The review identified many barriers to clinician and patient recruitment to randomised controlled trials confirming the persistent problems identified in other apparently less systematically conducted work 1, 2, 86.

The findings of our review should be read with some caution, however. In particular, several sources of potential bias are inherent in the material

Acknowledgements

Thanks to David Stephen and Neil Scott for assistance in reviewing the references, to Louise Smith for secretarial help, and to Sandra Kaiuka and Iain Colthart who conducted the original search and initial screening of papers. Carl Counsell was funded as a Wellcome Trust Training Fellow. The literature review was funded by the NHS Executive R&D Research Methodology Programme, and the Health Services Research Unit is core-funded by the Scottish Office Department of Health. However, the views

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