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Self-Report and Medication Possession Ratio are Accurate Measures of HIV Pre-Exposure Prophylaxis Use in a Real-World Clinical Setting
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IAS: HIV Prevention at IAS 2017 (PrEP) - Jared Baeten, MD PhD Connie Celum, MD MPH University of Washington (08/14/17)
IAS: PrEP at IAS 2017 / IAS Coverage: New HIV & HCV Drugs, Fatty Liver in HIV - (08/11/17)
Reported by Jules Levin
9th IAS Conference on HIV Science (IAS 2017), July 23-26, 2017, Paris
Rupa R. Patel1, Laura C. Harrison1, Albert Y. Liu2, Philip A. Chan3, Rachel Presti1, Peter L. Anderson4, Kenneth H. Mayer5, Sujata Patil6, William Powderly1, K. Rivet Amico7
1Washington University in St. Louis, 2San Francisco Department of Public
Health, 3The Miriam Hospital, 4University of Colorado, 5Fenway Institute,
6Memorial Sloan Kettering, 7University of Michigan
Abstract
Background: Oral, daily pre-exposure prophylaxis (PrEP) prevents HIV acquisition in optimally adherent men who have sex with men (MSM). Given the importance of adherence in PrEP-related outcomes, accurately and affordably monitoring adherence is a priority during implementation. We evaluated two low-burden measurements, self-report (SR) and medication possession ratio (MPR), for concordance with the well-established method of determining tenofovir diphosphate (TFV-DP) levels in dried blood spot (DBS).
Methods:
We reviewed behavioral and DBS data on patients presenting to the Washington University in St. Louis (USA) PrEP Clinic between November 2015 and August 2016. Optimal adherence was defined as TFV-DP ≥700 fmol/punch and was compared to patient 7-day SR and 3-month MPR using pharmacy refill data. Sensitivity, specificity, and negative and positive predictive value (NPV, PPV) for SR and MPR in relation to DBS were calculated.
Results: From 88 MSM, 137 DBS TFV-DP levels were analyzed. Their median age was 27 years; 58% were White, 30% Black, 6% Latino; 69% graduated college; and 71% reported condomless receptive anal sex in the last 3 months. Ten patients had a DBS < 700 fmol/punch. Drug concentration was not related to demography and did not significantly decline over time. By SR, 5 patients took < 4 doses/week, 4 of whom had sub-optimal DBS (NPV 80%), and of the 83 reporting ≥4 doses/week, 77 had optimal DBS (PPV 93%), resulting in 99% sensitivity and 40% specificity. For MPR, 3 patients had a MPR < 0.60 (indicating < 4 doses/week), all of whom had sub-optimal DBS (NPV 100%), and of the 84 with MPR ≥0.60, 77 had optimal DBS (PPV 92%), resulting in 100% sensitivity and 30% specificity. MPR and SR correlated with DBS TFV-DP levels (r=0.55, P< 0.001; r=0.48, P< 0.001). More stringent cut-offs to the strategies produced higher specificity- 60% for SR ≥6 doses/week and 70% for MPR at 0.70.
Conclusions: In a real-world clinical setting, SR and MPR correlated with optimal DBS concentrations despite different measurement windows (past 7, 30, 90 days). Specificity in this sample was improved when more stringent SR and MPR cut-offs were used. Results provide evidence for using low-burden measurements for PrEP adherence monitoring.
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