Among youth on PrEP, adherence waned over time. Self-report overestimated adherence, and use of Wisepill was limited. Hair collection was highly acceptable and provided similar interpretations to DBS. Incorporation of either metric in future PrEP studies among youth could identify suboptimal adherence and trigger interventions.

Objective The U.S. PrEP Demonstration Project (Demo) evaluated men-who-have-sex-with-men on pre-exposure prophylaxis (PrEP) post-marketing and found low seroconversion rates. The objective of this study is to examine hair levels as an adherence measure to PrEP. Design Using an “opt-in” design, participants of PrEP Demo were invited to enroll into a substudy where hair was collected quarterly. Methods Tenofovir concentrations were measured in hair by liquid-chromatography/tandem-mass-spectrometry. Hair levels consistent with ≥4 doses per week (protective in other studies) defined adequate adherence. Mixed effects multivariate logistic regression models examined factors associated with ≥4 doses/week. Separate mixed effects models evaluated the relationship between hair PrEP levels and changes in creatinine clearance (CrCl) over time. Results Overall, 58% of Demo participants enrolled into this opt-in study; reasons for non-participation included insufficient hair (61%) and concerns about hairstyle (27%). Hair and DBS levels consistent with ≥4 doses/week were highly concordant (84%). Hair levels showed adequate adherence in 87% of 875 person-visits (among 280 participants). Factors associated with adequate adherence in multivariate models were amphetamine use (aOR 2.59 (0.97–6.9, p 0.06), condomless receptive anal sex (aOR 2.28 (1.19–4.40, p 0.01), and stable housing (aOR 2.63 (1.03–6.67), p 0.04). Hair levels of tenofovir showed a monotonic relationship with decline in CrCl (p 0.01 for trend). Conclusions In this substudy of the PrEP Demonstration Project, hair and DBS levels were highly concordant and hair concentrations demonstrated adequate adherence 87% of the time, with stable housing and high-risk behavior associated with higher adherence. Daily PrEP drug-taking is associated with modest declines in CrCl.

Hair ART-concentrations were significantly associated with virologic outcomes among young people living with HIV. ART-concentration thresholds associated with virologic suppression are proposed. Hair analysis may provide a noninvasive, cost-effective adherence assessment tool in settings with limited second and third-line treatment options.

Objective: We examined the relationship between urine tenofovir (TFV) levels measured with a novel immunoassay, which permits point-of-care (POC) testing, with HIV seroconversion and objective adherence metrics in a large PrEP demonstration project.Design: Secondary analysis of stored specimens from an open-label PrEP cohort study Methods: We examined the association between undetectable urine TFV levels and HIV seroconversion in iPrEx-OLE using generalized estimating equations. We examined rank correlations between levels of TFV and emtricitabine (FTC) in urine, dried blood spots (DBS), and hair and determined the sensitivity and specificity of undetectable urine TFV for predicting dosing cut-offs in DBS. Results:The median urinary TFV level was 15,000 ng/ml in those who remained HIV-negative (n=105; IQR:1,000-45,000); 5,500 in those who eventually seroconverted (n=11; IQR:1,000-12,500); and all were undetectable at seroconversion (n=9; p<0.001). Decreasing strata of urine TFV levels were associated with future HIV seroconversion (p=0.03). An undetectable urine TFV was 100% sensitive and 81% specific when compared to an undetectable DBS TFV-DP level and 69% sensitive, but 94% specific, when compared to low adherence by DBS (<2 doses/week).Conclusions: Urine TFV detection by a novel antibody-based assay was associated with protection from HIV acquisition among individuals on PrEP. Urine TFV levels were correlated

Background: Objective adherence measures are of increasing interest in antiretroviral treatment (ART) monitoring. Hair ART levels predict virologic suppression and hair is easy to collect and store. No prior study has examined hair levels in an India-based cohort or laboratory. Methods: Small hair samples were collected from HIV-positive participants on either efavirenzbased or nevirapine-based ART in a South India-based study. Hair samples were split and analyzed for efavirenz or nevirapine in the UCSF-based Hair Analytical Laboratory (HAL) and the Division of Nutrition-analytic lab based at St. John's Research Institute (SJRI), Bangalore, India using liquid chromatography/tandem-mass-spectrometry. Agreement (using Bland-Altman methods) and rank correlation between the two laboratories' hair levels were calculated. Rank correlation between self-reported adherence (SRA) over the prior month using a visual analog scale and hair ART levels was calculated. Results: Among 75 participants (38 on nevirapine; 37 on efavirenz), the correlation between nevirapine levels generated by the two laboratories was 0.66 (p <0.0001) and between efavirenz levels was 0.87 (p <0.0001). Measurements from SJRI were usually within 20% of those from the