The effect of modest monetary incentives on follow-up rates in sexually transmitted disease studies

The purpose of the study was to determine if follow-up rates in sexually transmitted disease (STD) research could be improved by offering modest monetary incentives. Women aged 14-34, infected with Chlamydia trachomatis, and enrolled in either of 2 studies between May 1995 and January 1999 were included. Beginning in March 1996 participants were offered a $20 incentive to return to both the one- and four-month follow-up visits. Data were analysed using polychotomous logistic regression. Of 962 women followed, the majority (74.7%) received monetary incentives and 66% returned for at least one visit. Women who received the incentive were more likely (OR 1.9, CI 1.2-2.9) to return for either one or both of their follow-up visits after adjusting for interviewer and the months of work experience of that interviewer. Age and method of birth control were not associated with return rates. The study provides evidence that modest monetary incentives can improve follow-up rates.