Diagnostic accuracy of a point-of-care urine tenofovir assay, and associations with HIV viraemia and drug resistance among people receiving dolutegravir and efavirenz-based antiretroviral therapy

Introduction: Novel point-of-care assays which measure urine tenofovir (TFV) concentrations may have a role in improving adherence monitoring for people living with HIV (PLHIV) receiving antiretroviral therapy (ART). However, further studies of their diagnostic accuracy, and whether results are associated with viraemia and drug resistance, are needed to guide their use, particularly in the context of the global dolutegravir rollout.Methods: We conducted a cross-sectional evaluation among PLHIV receiving first-line ART containing tenofovir disoproxil fumarate at enrolment into a randomized trial in two South African public sector clinics. We calculated the diagnostic accuracy of the Abbott point-of-care immunoassay to detect urine TFV compared to liquid chromatography-tandem mass spectrometry (LC-MS/MS). We evaluated the association between point-of-care urine TFV results and self-reported adherence, viraemia >= 1000 copies/ml and HIV drug resistance, among people receiving either efavirenz or dolutegravir-based ART.Results: Between August 2020 and March 2022, we enrolled 124 participants. The median age was 39 (IQR 34-45) years, 55% were women, 74 (59.7%) were receiving efavirenz and 50 (40.3%) dolutegravir. The sensitivity and specificity of the immunoassay to detect urine TFV >= 1500 ng/ml compared to LC-MS/MS were 96.1% (95% CI 90.0-98.8) and 95.2% (75.3-100.0), respectively. Urine TFV results were associated with short (p<0.001) and medium-term (p = 0.036) self-reported adherence. Overall, 44/124 (35.5%) had viraemia, which was associated with undetectable TFV in those receiving efavirenz (OR 6.01, 1.27-39.0, p = 0.014) and dolutegravir (OR 25.7, 4.20-294.8, p<0.001). However, in those with viraemia while receiving efavirenz, 8/27 (29.6%) had undetectable urine TFV, compared to 11/17 (64.7%) of those receiving dolutegravir. Drug resistance was detected in 23/27 (85.2%) of those receiving efavirenz and only 1/16 (6.3%) of those receiving dolutegravir. There was no association between urine TFV results and drug resistance.Conclusions: Among PLHIV receiving ART, a rapid urine TFV immunoassay can be used to accurately monitor urine TFV levels compared to the gold standard of LC-MS/MS. Undetectable point-of-care urine TFV results were associated with viraemia, particularly among people receiving dolutegravir.