Barriers to participation in randomised controlled trials: a systematic review.

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.