Participation and retention in a study of female condom use among women at high STD risk.

PURPOSE: Differential participation and retention can bias the findings of a follow-up study. This problem was evaluated in a study of barrier contraception among women at high STD risk. The goal of this study was to identify predictors of participation and retention and determine whether they could influence study results. METHODS: Six-month follow-up study of women attending STD clinics. Determinants of participation and retention were evaluated using logistic and proportional hazards models. RESULTS: Agreement to participate was associated with young age, black race, low education and income, older age at first intercourse, the number of lifetime partners, and STD history. Early attrition was associated with young age, non-black race, higher income, lack of interest/commitment to using the female condom, high coital frequency, no STD history, not using a birth control method at baseline, and with inconsistent condom use, high coital frequency, and pregnancy during follow up. CONCLUSIONS: There was little evidence that differential participation influenced the validity of the study. Differential attrition may have biased behavioral measures of intervention effectiveness, but not necessarily measures of condom use effectiveness. (C) 2004 Elsevier Inc. All rights reserved.