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: ClinicalTrials.gov NCT02206555.
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PRELUDE Study Team Author Contributors Mark Bloch, Andrew Carr, Ching (Yvonne) Cheung (study clinical coordinator), Rosalind Foster, Christopher Gianacas (clinical data manager), Andrew Grulich, Rebecca Guy, Martin Holt, John Kaldor, Brent Mackie, Kenneth Mayer, John McAllister, Anna McNulty, Dean Murphy, Catriona Ooi, Cathy Pell, Isobel M. Poynten, Garrett Prestage, Nathan Ryder, David Templeton, Stefanie Vaccher (behavioural data manager), John de Wit, Edwina Wright, and Iryna Zablotska (chief investigator and protocol chair). NSW HIV Prevention Partnership Project Team Author Contributors Denton Callander, David Cooper, Craig Cooper, Levinia Crooks, Tim Duck, Andrew Grulich (principal investigator and protocol co-chair), Rebecca Guy, Jo Holden, Martin Holt, John Kaldor, Phillip Keen, Anthony Kelleher, Jo Mitchell, Garrett Prestage, Karen Price, Christine Selvey (principal investigator and protocol co-chair), Heather-Marie Schmidt, Barbara Telfer, Bill Whittaker, David Wilson, John de Wit and Iryna Zablotska. Participating clinics Clinic 16 at Royal North Shore Hospital, Holdsworth House Medical Practice, Newcastle Sexual Health Service, RPA Sexual Health, St Vincent’s Hospital HIV Immunology and Infectious Diseases Unit, Sydney Sexual Health Centre, Taylor Square Private Clinic, and Western Sydney Sexual Health Centre. Laboratories and clinical supplies Johns Hopkins Clinical Pharmacology Analytical Laboratory (CPAL, Baltimore, USA), St Vincent’s Centre for Applied Medical Research (AMR, Sydney, Australia), SydPath (Sydney, Australia). Community partner organisations ACON (AIDS Council of NSW) and Positive Life NSW.
This analysis was supported by funding from an NHMRC Partnership Project grant (Grant #1092852), the NSW Ministry of Health, and UNSW Sydney. An in-kind supply of study medication was provided by Gilead Sciences. The Kirby Institute receives funding from the Australian Government Department of Health and is affiliated with the Faculty of Medicine, UNSW Sydney.
Conflicts of interest
AEG has research funding from Seqirus, Gilead, Viiv, and in-kind research support from Hologic. He has received travel funding from Gilead. IBZ has received research funding and in-kind support (supply of the study medication) from Gilead Sciences Inc. Authors SJV, MAM, BGH, DJT, NR, AM, and RF declare that they have no conflicts of interest.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
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A list of other author contributors is included in the Acknowledgment section.
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Vaccher, S.J., Marzinke, M.A., Templeton, D.J. et al. Predictors of Daily Adherence to HIV Pre-exposure Prophylaxis in Gay/Bisexual Men in the PRELUDE Demonstration Project. AIDS Behav 23, 1287–1296 (2019). https://doi.org/10.1007/s10461-018-2353-5
- Pre-exposure prophylaxis (PrEP)
- Facilitated recall
- Blood tenofovir concentrations