Patterns of adherence among South African women in a phase III randomized controlled trial of a dapivirine vaginal ring for HIV-1 prevention


BACKGROUND: We explored dapivirine vaginal ring (DVR) adherence among South African women randomized to the active arm in the MTN-020/ASPIRE phase III, randomized placebo-controlled trial (NCT01617096) to understand adherence patterns in the last year of follow-up and identify characteristics influencing adherence.
METHODS: Acetone extraction and high-pressure liquid chromatography were used to measure remaining dapivirine in returned rings of study participants. A monthly adherence measure was defined as the ratio of dapivirine released to the number of days since ring dispensation. High adherence was defined as '¥4 mg dapivirine released per month. Enrollment start times differed across countries, hence the analysis only included women enrolled in South Africa (n=626). We used group-based trajectory modeling to identify clusters of participants with similar longitudinal patterns of adherence during their last year of ring use and potential predictors of group membership.
RESULTS: Women were on average aged 25 at enrollment (range 18-44 years) and were followed for a median of 26 months (range 12-33). Five adherence patterns were identified, see Figure 1: (1) consistently high, [34%], (2) consistently moderate [34%], (3) increasing [7%], (4) decreasing [9%], (5) consistently low [16%]. Women classified as high adherers (1) were more likely to be older (>21 years) compared to low adherers (5) [OR 1.87, 95% CI: 1.10, 3.18], parous compared to decreasing adherers (4) [OR 3.57, 95% CI: 1.58, 8.02] and less likely to have completed secondary education compared to moderate adherers (2) [OR 0.59, 95% CI: 0.38, 0.92]. Income, alcohol use, and condom use were not associated with adherence group classification (p'¥0.30).

CONCLUSIONS: Most South African women successfully persisted with at least some ring use during their last year in the trial. Young and nulliparous women may benefit from additional targeted adherence support efforts in future ring trials.