Predictors of Adherent Use of Diaphragms and Microbicide Gel in a Four-Arm, Randomized Pilot Study Among Female Sex Workers in Madagascar

Abstract

Participants' protocol adherence may influence assessments of the effectiveness of new female-controlled methods for sexually transmitted infection prevention. In 2005 we conducted a randomized pilot study among female sex workers (FSWs) in Madagascar in preparation for sexually transmitted infection prevention trial of diaphragms and a vaginal microbicide. Participants (n = 192) were randomized into 4 arms: diaphragm plus microbicide (Acidform), diaphragm plus placebo gel hydroxyethyl cellulose (HEC), Acidform alone, or HEC alone. FSWs were seen weekly for 4 weeks. Using multivariable regression with generalized estimating equations, we assessed predictors of adherent product use during all sex acts in the last week. We collapsed the gel-diaphragm arms together and the gel-only arms together for this analysis. Between 43% and 67% of gel-diaphragm users (varying by visit) reported using study products during all sex acts in the last week, compared with 20% to 45% of gel-only users. Adherence increased with follow-up [visit 4 vs. visit 1 risk ratio (RR) for gel-diaphragm users: 1.55, P <0.01; for gel-only users, RR: 1.58, P = 0.01]. Gel-diaphragm users whose casual partners were never aware of products (RR: 2.02, P = 0.03) and who had experienced partner violence after requesting condom use (RR: 1.45, P <0.01) were more adherent. Gel-only users reporting lower sexual frequency (1-9 weekly acts vs. >or=19 acts, RR: 1.98, P <0.01) and no sex with primary partners in the past week (RR: 1.54, P = 0.02) were more adherent. Gel-diaphragm users had better adherence than gel-only users, and predictors of adherence differed between groups. Addressing modifiable factors during counseling sessions may improve adherence.