A simple, quick point-of-care urine test for tenofovir adherence, similar to an OTC-pregnancy test, has an accuracy of 99.6% versus laboratory testing, according to a report at the Conference on Retroviruses & Opportunistic Infections.
A few drops of urine yield results in 5 minutes, and tell if patients have been taking tenofovir, a key component of HIV preexposure prophylaxis (PrEP) medications, within the previous 4-7 days. Abbott Rapid Diagnostics is gearing up to market the test widely in the United States, and it won’t be very expensive, according to lead investigatora clinical fellow and HIV/AIDS researcher at the University of California, San Francisco.
It’s an alternative to the usual approach, measuring tenofovir levels in hair, blood, or urine by liquid chromatography and mass spectrometry. That approach is expensive and requires trained personnel, and the results can take a while. Dr. Spinelli and colleagues saw the need for a quicker, easier way for use in the clinic, since real-time adherence results are most likely to make a difference, he said at the meeting, which was scheduled to be in Boston, but was held online instead this year because of concerns about spreading the COVID-19 virus.
Self-report, meanwhile, is notoriously unreliable. Over 90% of people in two previous PrEP studies said they were taking their medications, but only about a quarter had tenofovir in their plasma.
The investigators identified a tenofovir antibody in urine that could be read by enzyme-linked immunosorbent assay (ELISA), and validated it for adherence accuracy against liquid chromatography and mass spectrometry; they then put the antibody on a test strip to create a lateral flow immunoassay.
After hearing the presentation, moderatordirector of HIV prevention research at the San Francisco Department of Public Health, called the work “important” and said it “really has the possibility of opening up a lot of new kinds of studies and new kinds of intervention for both prevention and treatment.”
Dr. Spinelli and colleagues pitted the test strip against their laboratory-based ELISA test using 684 stored urine samples from 324 men and women in disoproxil fumarate/emtricitabine (Truvada) PrEP projects in Africa and the United States.
Overall, the 505 samples that were positive for tenofovir in the lab test were also positive on the urine strip, yielding 100% sensitivity. Of the 179 negative samples on the lab test, 176 were also negative with the strip, yielding a specificity of 98.3%. The results calculated into nearly perfect accuracy.
“We believe that” the urine test strip “is ready for field testing,” and that “point-of-care adherence testing” will be a boon to both PrEP and HIV treatment. A negative test, for instance, would signal the need for immediate counseling, and the patient would still be in the office to hear it. For HIV, high adherence but also high viral load would signal the need for resistance testing, Dr. Spinelli said.
A white-coat effect is possible; people might take their medication when they know they have an upcoming doctor’s appointment. “We will need to evaluate for [that] with additional studies” comparing point-of-care testing with longer-term metrics, such as drug levels in hair, he said.
The study was published to coincide with Dr. Spinelli’s report (J Acquir Immune Defic Syndr. 2020 Mar 10. doi:).
The funding source wasn’t reported. Dr. Spinelli had no disclosures. Two investigators were Abbott employees.
SOURCE: Spinelli MA et al. 2020 .