Study Product Adherence Measurement in the iPrEx Placebo-Controlled Trial: Concordance With Drug Detection. Our objective was to evaluate the concordance between adherence estimated by self-report (in-person interview or computer-assisted self-interview), in-clinic pill counts, and pharmacy dispensation records and drug detection among participants in a placebo-controlled pre-exposure prophylaxis HIV prevention trial (iPrEx). Cross-sectional evaluation of 510 participants who had drug concentration data and matched adherence assessments from their week-24 study visit. Self-reported adherence collected through (1) interview and (2) computer-assisted self-interview surveys, (3) adherence estimated by pill count, and (4) medication possession ratio was contrasted to having a detectable level of drug concentrations [either tenofovir diphosphate (TFV-DP) or emtricitabine triphosphate (FTC-TP)], as well as to having evidence of consistent dosing (tenofovir diphosphate ≥ 16 fmol/10 cells), focusing on positive predictive values, overall and by research site.
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