Researchers have developed a urine test that can determine adherence to Truvada (tenofovir disoproxil fumarate/emtricitabine) as pre-exposure prophylaxis (PrEP). If ultimately developed commercially, such a test could provide PrEP providers with a simple way to monitor HIV-negative individuals on Truvada for adherence to the daily regimen and to offer support to encourage better adherence if necessary.
The investigators developed a urine assay to detect levels of the metabolized form of the tenofovir disoproxil fumarate component of Truvada. When metabolized, the drug is known simply as tenofovir, or TFV.
To determine how well the urine test detects TFV, the researchers studied its response to urine samples from three research groups of 10 people each between January and December 2014.
The first was a group of people living with HIV who reported excellent adherence to an antiretroviral (ARV) regimen that included Truvada and who had an undetectable viral load. These individuals kept a diary of the date and time of their ARV doses for the week leading up to giving a blood and urine sample—which took place within a four-week window following an undetectable result on a viral load test. The researchers used the data gathered from this group to determine the relationship between the test results on the urine and blood tests.
The second group included 10 HIV-negative people who received a single dose of Truvada under direct supervision. These individuals gave blood and urine samples each day for seven days so the researchers could estimate the relationship between the level of detectable TFV in urine and the interval (of up to seven days) since an individual last took Truvada.
The third group included 10 HIV-negative individuals who were prescribed daily Truvada as PrEP for 24 weeks. They provided urine samples weekly and blood samples monthly to give the researchers information about their adherence and the connection between urine and blood sample results. At each study visit, the participants provided a report of the last date and time they took Truvada.
The investigators found that the urine test detected TFV with greater sensitivity than the blood test and that it had a detection window of seven days since the last dose. The test could distinguish high and low adherence patterns with the last 48 hours as well as nonadherence stretching back seven days.
To read the study abstract, click here.