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Brief Report

Validation of a Urine Tenofovir Immunoassay for Adherence Monitoring to PrEP and ART and Establishing the Cutoff for a Point-of-Care Test

Gandhi, Monica, MD, MPHa; Bacchetti, Peter, PhDb; Spinelli, Matthew A., MDa; Okochi, Hideaki, PhDc; Baeten, Jared M., MD, PhDd; Siriprakaisil, Oraphan, MDe; Klinbuayaem, Virat, MDe; Rodrigues, Warren C., MSf; Wang, Guohong, PhDf; Vincent, Michael, MSf; Cressey, Tim R., PhDg,h,i; Drain, Paul K., MDd

JAIDS Journal of Acquired Immune Deficiency Syndromes: May 1, 2019 - Volume 81 - Issue 1 - p 72–77
doi: 10.1097/QAI.0000000000001971
Clinical Science

Background: Current pharmacologic adherence monitoring for antiretrovirals involves expensive, labor-intensive liquid chromatography/tandem mass spectrometry (LC-MS/MS)-based methods. Antibody-based assays can monitor and support adherence in real time. We developed a tenofovir (TFV)-based immunoassay and further validated it in a directly observed therapy (DOT) study.

Design: Pharmacologic DOT study of TFV disoproxil fumarate (TDF)/emtricitabine (FTC) administered to HIV-noninfected volunteers.

Methods: The TARGET study provided directly observed TDF 300 mg/FTC 200 mg 7 (high adherence), 4 (moderate), and 2 doses/week (low) to 30 volunteers (10/group) in Thailand, collecting a total of 637 urine samples over 6 weeks of administration and during washout. ELISA measured urine TFV levels by the immunoassay and LC-MS/MS-based concentrations served as the gold standard. A mixed-effects regression model evaluated cutoffs for a point-of-care assay. Performance characteristics of the immunoassay were compared with LC-MS/MS at a chosen cutoff.

Results: Median TFV levels were 12,000 ng/mL by the immunoassay 1 day after dosing; 5000 ng/mL 2 days after dosing; 1500 ng/mL 3 days after dosing; and below the lower limit of quantification thereafter (≥4 days). An immunoassay cutoff of 1500 ng/mL accurately classified 98% of patients who took a dose 24 hours ago as adherent. The specificity and sensitivity of the immunoassay compared with LC-MS/MS at the 1500 ng/mL cutoff were 99% and 94%; the correlation between TFV levels by the 2 assays was high (0.92, P < 0.00001).

Conclusions: We have developed a novel TFV immunoassay that is highly specific, sensitive, and correlates strongly with LC-MS/MS measurements in a large DOT study. Adherence benchmarks from this DOT study will guide the development of a low-cost rapid point-of-care test for pre-exposure prophylaxis and antiretroviral treatment adherence monitoring and interventions.

aDivision of HIV, Infectious Disease, and Global Medicine, Department of Medicine, University of California, San Francisco (UCSF), San Francisco, CA;

Departments of bEpidemiology and Biostatistics; and

cBioengineering and Therapeutic Sciences, UCSF, San Francisco, CA;

dDepartments of Global Health, Medicine and Epidemiology, University of Washington, Seattle, WA;

eDepartment of Medicine, Sanpatong Hospital, Sanpatong, Chiang Mai, Thailand;

fImmunoanalysis Division, Alere Rapid Diagnostics, Abbott Rapid Diagnostics Division (ARDx), Pomona, CA;

gDepartment of Medicine, Chiang Mai University, Chiang Mai, Thailand;

hDepartment of Immunology and Infectious Diseases, Harvard T.H Chan School of Public Health, Boston, MA; and

iDepartment of Molecular and Clinical Pharmacology, University of Liverpool, United Kingdom.

Correspondence to: Monica Gandhi, MD, MPH, Medicine, Division of HIV, Infectious Diseases, and Global Medicine, 995 Potrero Avenue, 4th floor, Room 423D, San Francisco, CA 94110 (e-mail:

M.G. received 2 grants from the NIH supporting this work, including the development of the antibody at Alere Rapid Diagnostics (R01AI143340 and 2RO1AI098472). P.K.D. received 2 grants from the NIH that helped support this work (R21AI127200 and R01AI136648). Funding for this work and the development of the antibody at Alere Rapid Diagnostics was provided by the National Institute of Allergy and Infectious Diseases/National Institutes of Health (NIAID/NIH) R01AI143340 (P.I. Gandhi). Three authors (W.C.R., G.W., and M.V.) as indicated on the title page are from Alere Rapid Diagnostics company. Further funding from this work came from NIAID/NIH 2RO1AI098472 (P.I. Gandhi); R21AI127200 and R01AI136648 (P.I. Drain). M.A.S. was supported by T32AI060530 (P.I. Havlir).

M.V., G.W., and W.C.R. are all employed by Alere Rapid Diagnostics. The remaining authors have no funding or conflicts of interest to disclose.

Received November 13, 2018

Accepted December 21, 2018

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