Recruiting patients to randomized trials in primary care: principles and case study

Background. There are many factors affecting recruitment to trials in primary care, and trials are often jeopardized due to the inability to enter sufficient patient numbers. It is generally agreed that the interest in and commitment of GPs to the project are important, and their forgetfulness and time pressures are major factors which mitigate against maximal recruitment. Objectives. The aim of this study is to focus on maximizing recruitment of patients to a randomized controlled trial of exercise classes for back pain patients. Methods. Two distinct methods of recruitment were used. One practice provided a computerized list of names and asked patients' permission, by letter, to be contacted by the researchers. The other 18 practices manually recorded referrals after the consultation by the GP. Results. Referral rates were slower than expected. Many patients either did not fit the inclusion criteria or excluded themselves due to domestic commitments or work. During 24 months, 1588 patients were referred. A total of 187 patients (12%) met the criteria and could be included in the study. The practice which referred patients through a computerized listing contributed 44% of the patients successfully included in the study. Conclusions. Recruitment rates depended on the method and rate of GP referrals, the proportion of referrals meeting the entry criteria and the proportion of patients available to attend the exercise classes.