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  • PMID: 30865174 was deleted because it is a duplicate of PMID: 31095005
J Acquir Immune Defic Syndr. 2019 Jun 1;81(2):158-162. doi: 10.1097/QAI.0000000000002005.

Brief Report: Short-Term Adherence Marker to PrEP Predicts Future Nonretention in a Large PrEP Demo Project: Implications for Point-of-Care Adherence Testing.

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Division of HIV, ID, and Global Medicine, University of California, San Francisco, CA.
Department of Epidemiology and Biostatistics, University of California, San Francisco, CA.
Department of Pharmaceutical Sciences, University of Colorado, Aurora, CO.
San Francisco Department of Public Health, San Francisco, CA.
Department of Clinical Investigations, Whitman-Walker Health, Washington, DC.
Department of Medicine, University of Miami Miller School of Medicine, Miami, FA.



Objective adherence metrics for tenofovir (TFV) disoproxil fumarate/emtricitabine (FTC)-based pre-exposure prophylaxis (PrEP) were critical for interpretation of efficacy in PrEP clinical trials, and there is increasing interest in using drug levels to tailor interventions for reengagement and adherence. Point-of-care immunoassays for TFV, which examine short-term adherence, are in development. However, the ability of poor short-term and long-term adherence to predict future PrEP nonretention is unknown.


Secondary data analysis of a large, prospective multi-site U.S. PrEP demonstration project.


An adjusted Cox-proportional hazards model examined the relationship of dried blood spot (DBS) levels of FTC-triphosphate (FTC-TP) or TFV-diphosphate (TFV-DP), measures of short-term and long-term PrEP adherence, respectively, with future study nonretention.


Overall, 294 individuals (median age 33 years) contributed drug levels within the U.S. PrEP demonstration project. By the end of study, 27% were lost to follow-up, 25% had at least one undetectable FTC-TP level indicating poor short-term adherence, and 29% had a drug level indicating suboptimal long-term adherence (TFV-DP <700 fmol/punch). The strongest factor associated with future study nonretention using a binary drug-level cut-off was an undetectable DBS FTC-TP level (adjusted hazard ratio 6.3; 95% confidence interval 3.8 to 10.2). The suboptimal long-term adherence based on low DBS TFV-DP levels was also associated with nonretention (adjusted hazard ratio 4.3; 95% confidence interval: 2.4 to 7.6).


Both short- and long-term metrics of PrEP adherence are strongly associated with future loss to follow-up in a U.S. demonstration project study. Short-term metrics of adherence, once available at the point-of-care, could be used to direct real-time tailored retention and adherence interventions.

[Available on 2020-06-01]

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