Accuracy of PrEP adherence measures among adolescents men who have sex with men and transgender women in Brazil

Title

Accuracy of PrEP adherence measures among adolescents men who have sex with men and transgender women in Brazil

Presenter

Diana Zeballos

Authors

D. Zeballos * (1), F. Soares (1), L. Magno (2), M. Eustorgio (3), L. Amorim (1), I. Dourado (1), The PrEP1519 Brazil Study Group

Institutions

(1) Federal University of Bahia, Collective Health Institute, Salvador, Brazil, (2) State University of Bahia, Salvador, Brazil, (3) Federal University of Bahia, Institute of Mathematics and Statistics, Salvador, Brazil

BACKGROUND: Adherence is fundamental to PrEP effectiveness. Direct measures of adherence are expensive and not sustainable in most PrEP services. Therefore, an indirect measure is a feasible alternative. The aim of this analysis was to assess the concordance of indirect measures for PrEP adherence comparing them with a direct measure.
METHODS: PrEP1519 is a daily PrEP demonstration cohort study among adolescent men who have sex with men (aMSM) and transgender women (aTGW) aged 15-19 years. Indirect measures such as medication possession ratio (MPR), pill-count, and self-report were compared to tenofovir diphosphate (TFV-DP) concentrations in dried blood spot (DBS). Participants receiving pills of FTC/TDF, had DBS collected and stored at each study visit, were asked to return their PrEP bottles and to recall PrEP use in the last 30 days. A sample of DBS from aMSM, DBS from all seroconverters, and all aTGW were sent for quantification of TFV-DP concentrations. The accuracy of each indirect measure was assessed using Areas under (AUC) the receiver operating characteristics (ROC) curves for protective TFV-DP levels '¥800fmol/punch equivalent to 4 doses per week or above. Sensitivity (SE), specificity (SP), and predictive values positive (PPV) and negative (NPV) were assessed for the best cutoff points identified by Youden index.
RESULTS: DBS data from 188 participants were included. Coincidental data for indirect measures were: MPR (N=185), pill-count (N= 68) and self-report (N= 174). The AUC was 0.55 (95%CI: 0.47'0.53) for MPR, AUC = 0.67 (95%CI: 0.54'0.80) for pill count, and AUC = 0.72 (95%CI: 0.65'0.80) for self-report. The best cut-off point was 0.90 for MPR with 80.3% SE, 40.4% SP, 25.4% PPV and 51.6% NPV; for pill count was 92.7% with 72.7% SE, 62.9% SP, 29.0% PPV and 35.1% NPV and 83.3% for self-report with 91.8% SE, 46.5% SP, 11.3% PPV and 44.6% NPV.
CONCLUSIONS: Pill count and self-report were able to discriminate adolescents with protective levels of TFV-DP. In addition, self-report adherence showed the best performance, and it is feasible and sustainable to be implemented in PrEP services for adolescents.

Download the e-Poster (PDF)