Methods to maximize retention in weight loss studies

Objective: Dropouts from clinical trials decrease quality and increase cost s. Free participation, paid participation, and contingency contracting are three study retention methods. Contingency contracting, or depositing a fee to be refunded contingent upon attendance in a clinical trial, has been re ported to decrease dropouts without affecting weight loss. These three meth ods of retention were compared with a commercial weight loss clinic's pract ice of charging non-refundable fees. Methods and Procedures: Dropouts were compared in two studies testing mazin dol, with one study using free care and the other using contingency contrac ting; two studies testing phenylpropanolamine, one using free care and the other using contingency contracting; and in studies with phenylpropanolamin e on file with Thompson Medical Company using free care, paid participation , and contingency contracting. Results: The dropout rate was 50% at 8 weeks in a trial of mazindol with fr ee care vs. 7% for contingency contracting (p<0.001). The two phenylpropano lamine studies gave the same weight losses, but the dropouts were 37% at 8 weeks for free care vs. 11% for contingency contracting (p<0.001). The stud ies of phenylpropanolamine on file at the Thompson Medical Company had 28% dropouts at 8 weeks using free care vs. 19% for paid participation (p<0.001 ), and 11% for contingency contracting (p<0.005). Dropouts with contingency contracting (11%) were not different from the commercial weight loss progr am (13%). Discussion: Contingency contracting can decrease dropouts, improve quality, and decrease costs without affecting weight loss in clinical trials for ob esity.