Urine as a Biomarker for Adherence

Adherence is critical for PrEP and ART efficacy but no current real-time metric of adherence to antiretrovirals (ARVs) at the point of care yet exists. The current techniques to measure antiretrovirals (ARVs) in hair and other biomatrices, such as plasma and dried blood spots, require spectrometry machines and specialized personnel. The UCSF Hair Analytical Laboratory (HAL) has expertise in hair metrics of adherence. However, antibody-based tests (lateral flow immunoassays)1,2 are low-cost, enable drug detection to occur within minutes, and can be performed by non-trained personnel, research participants or patients after self-collection.3 The most well-known lateral flow immunoassay is the urine-based pregnancy test.

The UCSF HAL has now developed a collaboration with Abbott/Alere™ Rapid Diagnostics, a company with vast expertise in point of care (POC) assays, to develop an immunoassay that quantitates TFV levels in urine.4-8 The test is sensitive (96%), specific (100%), precise (coefficient of variation <15%), and quantitates TFV levels in urine as accurately as LC-MS/MS (correlation between TFV levels by both assays 0.96) in a study of HIV-negative patients taking PrEP with TDF/FTC.4 There are high levels of agreement between the levels produced by the assay and LC-MS/MS (using Bland Altman methods).4,5

Moreover, we have also demonstrated that low levels of TFV by this urine assay predict future PrEP seroconversion in a large demonstration project (iPrEx Open Label Extension study).6 Finally, we have determined the appropriate adherence cut-off for the POC urine assay (lateral flow assay) using samples from a directly-observed therapy study where TDF/FTC was administered to HIV-noninfected volunteers.5 This cut-off minimizes misclassification of adherence and the assay has now being translated to a corresponding lateral flow assay7 for POC adherence testing (Figure 1) in a variety of studies. The performance of the LFA in diverse populations, when compared to both LC-MS/MS and traditional enzyme-linked immunoassay (ELISA), has been excellent.7,8

Compared to other biomatrices, urine collection is non-invasive and can be readily self-collected. Studies have shown that TFV in urine is stable at room temperature for up to seven days9 and also in cryopreserved specimens. As TFV is used in the backbone of most HIV treatment regimens worldwide, either in the form of TDF10 or tenofovir alafenamide (TAF), urine monitoring of TFV would assess adherence on most HIV treatment regimens and on TDF/FTC or TAF/FTC-based PrEP. Moreover, POC urine testing strips can be mailed to participants with instructions for collecting the urine and conducting the assay (similar to a home pregnancy test). in order to help motivate adherence or record adherence for research studies. The test, when marketed, will be low cost, easy to perform and assesses short-term adherence (over 4 days) within 5 minutes. The assay is now ready for research studies through the UCSF HAL to further evaluate its use in PrEP and ART studies.

Fig. 1. Prototype of urine-based point of care rapid testing strip

References:

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  3. Bang HI, Jang MA, Lee YW. Evaluation of the Triage TOX Drug Screen Assay for Detection of 11 Drugs of Abuse and Therapeutic Drugs. Ann Lab Med. 2017;37(6):522-525.
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  5. Gandhi M, Bacchetti P, Spinelli MA, et al. 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. J Acquir Immune Defic Syndr. 2019;81(1):72-77.
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  8. Spinelli MA, Rodrigues WC, Wang G, Vincent M, Glidden DV, Okochi H, Stalter R, Defechereux P, Deutsch M, Grant RM, Ngure K, Mugo NR, Baeten JM, Gandhi M. High accuracy of a real-time urine antibody-based tenofovir point-of-care test compared to laboratory-based ELISA in diverse populations. JAIDS 2020 (in press)
  9. Koenig HC, Mounzer K, Daughtridge GW, et al. Urine assay for tenofovir to monitor adherence in real time to tenofovir disoproxil fumarate/emtricitabine as pre-exposure prophylaxis. HIV Med. 2017;18(6):412-418.
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