We examined the relationship between urine tenofovir (TFV) levels measured with a novel immunoassay, which permits point-of-care testing, with HIV seroconversion and objective adherence metrics in a large preexposure prophylaxis (PrEP) demonstration project.
Secondary analysis of stored specimens from an open-label PrEP cohort study.
We examined the association between undetectable urine TFV levels and HIV seroconversion in iPrEx open-label extension using generalized estimating equations. We examined rank correlations between levels of TFV and emtricitabine 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.
The median urinary TFV level was 15 000 ng/ml in those who remained HIV-negative (n = 105; interquartile range: 1000–45 000); 5500 in those who eventually seroconverted (n = 11; interquartile range: 1000–12 500); 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 with an undetectable DBS TFV-diphosphate level and 69% sensitive, but 94% specific when compared with low adherence by DBS (<2 doses/week).
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 with hair and DBS levels and undetectable urine TFV was 100% sensitive in detecting nonadherence. By implementing the immunoassay into a point-of-care strip test, PrEP nonadherence could be detected in real-time, allowing rapid intervention.
aDivision of HIV, ID, and Global Medicine
bDepartment of Epidemiology and Biostastistics, University of California, San Francisco, San Francisco
cAlere Rapid Diagnostics/Abbott Rapid Diagnostics Division, Pomona
dDepartment of Bioengineering and Therapeutic Sciences
eDepartment of Medicine, University of California, San Francisco
fBridge HIV, San Francisco Department of Public Health, San Francisco, California, USA.
Correspondence to Matthew A. Spinelli, MD, Division of HIV, ID, and Global Medicine, Zuckerberg San Francisco General Hospital/University of California, San Francisco, 995 Potrero Avenue, Ward 84, San Francisco, CA 94110, USA. E-mail: Matthew.Spinelli@UCSF.edu
Received 9 October, 2018
Revised 4 December, 2018
Accepted 15 December, 2018
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