Evaluation of a Run-In Period to Improve Participant Retention in a Behavioral Intervention to Improve Blood Pressure Control

Dropouts reduce the validity of results obtained from randomized clinical trials (RCT). Thus it is critical to retain patients once randomized. We evaluated the usefulness of a run-in period to reduce the number of dropouts in a behavioral intervention to improve blood pressure. In the pilot study where a run-in period was not used, we had a 29% dropout rate. A prospective evaluation was performed in the context of a 3-arm RCT. Patients are approached during a routine visit, informed about the study, and invited to participate if eligible. After a 1-month run-in period, patients return for a baseline visit. They are then randomly assigned to the usual care, health education intervention, or stage of change matched intervention groups. Participants are followed for 1 year (they make 4 total visits). We identified 3646 potential participants by medical record review of which 2730 made the actual visit. Of these 2730, 1181 were interested enough to get detailed information about the study; the remaining were not interested (82), had no time (119), were missed (679), or were ineligible (669). Of the 1181 informed, 279 consented, and 188 were subsequently enrolled. Prior to the baseline visit, 49 patients withdrew consent, 100 were randomized and 4 dropped out. In our study to date, while our cancellation rate is 26%, our drop out rate is only 4%. This is much better than most behavioral trials. We believe that the run-in period has allowed us to reduce the number of dropouts after randomization.