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Randomized Controlled Trial
. 2015 Jan 1;68(1):13-20.
doi: 10.1097/QAI.0000000000000386.

Comparing the novel method of assessing PrEP adherence/exposure using hair samples to other pharmacologic and traditional measures

Sanjiv M Baxi  1 , Albert Liu, Peter Bacchetti, Gaudensia Mutua, Eduard J Sanders, Freddie M Kibengo, Jessica E Haberer, James Rooney, Craig W Hendrix, Peter L Anderson, Yong Huang, Frances Priddy, Monica Gandhi
Affiliations
Free PMC article
Randomized Controlled Trial

Comparing the novel method of assessing PrEP adherence/exposure using hair samples to other pharmacologic and traditional measures

Sanjiv M Baxi et al. J Acquir Immune Defic Syndr. .
Free PMC article

Abstract

Objective: The efficacy of pre-exposure prophylaxis (PrEP) in HIV will diminish with poor adherence; pharmacologic measures of drug exposure have proven critical to PrEP trial interpretation. We assessed drug exposure in hair against other pharmacologic and more routinely used measures to assess pill-taking.

Design: Participants were randomized to placebo, daily PrEP, or intermittent PrEP to evaluate safety and tolerability of daily versus intermittent tenofovir/emtricitabine (TFV/FTC) in 2 phase II PrEP clinical trials conducted in Africa. Different measures of drug exposure, including self-report, medication event monitoring system (MEMS)-caps openings, and TFV/FTC levels in hair and other biomatrices were compared.

Methods: At weeks 8 and 16, self-reported pill-taking, MEMS-caps openings, and TFV/FTC levels in hair, plasma, and peripheral blood mononuclear cells (PBMCs) were measured. Regression models evaluated predictors of TFV/FTC concentrations in the 3 biomatrices; correlation coefficients between pharmacologic and nonpharmacologic measures were calculated. Both trials were registered on ClinicalTrials.gov (NCT00931346/NCT00971230).

Results: Hair collection was highly feasible and acceptable (100% in week 8; 96% in week 16). In multivariate analysis, strong associations were seen between pharmacologic measures and MEMS-caps openings (all P < 0.001); self-report was only weakly associated with pharmacologic measures. TFV/FTC hair concentrations were significantly correlated with levels in plasma and PBMCs (correlation coefficients, 0.41-0.86, all P < 0.001).

Conclusions: Measuring TFV/FTC exposure in small hair samples in African PrEP trials was feasible and acceptable. Hair levels correlated strongly with PBMC, plasma concentrations, and MEMS-caps openings. As in other PrEP trials, self-report was the weakest measure of exposure. Further study of hair TFV/FTC levels in PrEP trials and demonstration projects to assess adherence/exposure is warranted.

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Figures

FIGURE 1
FIGURE 1
Demonstration of hair sampling in African patient (patient consent provided).
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References

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