Predictors of Daily Adherence to HIV Pre-exposure Prophylaxis in Gay/Bisexual Men in the PRELUDE Demonstration Project

Stefanie J. Vaccher, Mark A. Marzinke, David J. Templeton, Bridget G. Haire, Nathan Ryder, Anna McNulty, Rosalind Foster, Andrew E. Grulich, Iryna B. Zablotska, on behalf of the PrELUDE Study Group, the NSW HIV Prevention Partnership Project

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Adequate adherence to pre-exposure prophylaxis (PrEP) is critical to prevent HIV infection, but accurately measuring adherence remains challenging. We compared two biological [blood drug concentrations in plasma and peripheral blood mononuclear cells (PBMC)] and two self-reported measures (facilitated recall to clinicians and self-report in online surveys) and identified predictors of daily PrEP adherence among gay and bisexual men (GBM) in their first 12 months on PRELUDE, an open-label, single-arm PrEP demonstration project in New South Wales, Australia. 327 participants were enrolled; 263 GBM attended their 12-month follow-up visit (81% retention). Overall, 91% of blood samples had plasma drug concentrations indicative of taking 7 pills/week, and 99% had protective drug concentrations (≥ 4 pills/week). Facilitated recall to clinicians identified 99% of participants with protective adherence as measured by PBMC drug concentrations. Daily adherence measured by facilitated recall was associated with behavioural practices including group sex (aOR 1.33, 95% CI 1.15–1.53, p < 0.001). Retained participants maintained high adherence to daily PrEP over 12 months, confirmed by four different measures. Facilitated recall to clinicians is a suitable measure for assessing PrEP adherence in populations engaged in care where there is established trust and rapport with patients. Trial registration: NCT02206555.

Original languageEnglish
Pages (from-to)1287-1296
Number of pages10
JournalAIDS and Behavior
Issue number5
Publication statusPublished - May 2019
Externally publishedYes


  • Adherence
  • Blood tenofovir concentrations
  • Facilitated recall
  • HIV
  • Pre-exposure prophylaxis (PrEP)

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