Recruitment of participants for the multiple risk factor intervention trial (MRFIT).

The Multiple Risk Factor Intervention Trial (MRFIT) was a randomized primary prevention trial designed to test the effect of multifactor intervention on mortality from coronary heart disease. Before randomization, men were seen at three screening visits to establish eligibility. A total of 361,662 men were screened, and 12,866 men were randomized, 866 more than the goal of 12,000. The total time required for planning and recruitment was 44 months. Eligibility rates and dropout or refusal rates between screening visits varied considerably among the 20 clinics that took part in MRFIT. The variation in eligibility rates resulted largely from subjective interpretation by the staff of the willingness of the men to participate in the study and to make risk factor changes. Cigarette smokers and blacks were more likely to discontinue their participation between screening exams. The ultimate success of the MRFIT recruitment is attributed to (1) the previous experience of investigators in screening large numbers of participants for clinical trials and similar epidemiologic investigations, (2) the identification at each clinic of one or more persons whose specific responsibility was recruitment, (3) the phased entry of clinics into the study, (4) routine monitoring and reporting of recruitment rates by the coordinating center, (5) regular discussion of recruitment successes and problems at the Steering Committee meetings, and (6) site visits to examine in detail recruitment problems.