A sensitivity analysis should be considered, with indicative estimates rather than unrealistically precise numbers. Small trials should be reported as hypothesis forming. To overcome barriers to clinician recruitment, a trial should address an important research question and the protocol and data collection should be as straightforward as possible, with demands on clinicians and patients kept to a minimum. Dedicated research staff may be required to support clinical staff and patients. The recruitment aspects of an RCT should be carefully planned and piloted.
Many trials fail to start, mainly because of lack of funding or logistical problems.
Of those that start, half have recruitment difficulties, leading to abandonment or reduced size and, hence, loss of statistical power. Recruitment problems may be reduced by piloting, using multiple recruitment strategies, making contingency plans in case recruitment is slow, and using recruitment coordinators. None of these approaches has been rigorously evaluated. Quality control is important but too much may make RCTs prohibitively expensive and hinder recruitment. Trials need good organisational and administrative bases but there is little research evaluating the optimal structure.