This is the first study to investigate the use of FPT in ART-treated subjects and demonstrates that it may provide a practical, reliable method for virologic monitoring in resource-poor settings. Plasma FPT was accurate but requires centrifuge; whole blood produced a high number of false-positive results, but these were low-level. Whole blood may be sufficiently accurate if higher HIV RNA cut-offs were used to define virologic failure.

BackgroundRoutine viral load monitoring of patients on antiretroviral therapy (ART) is not affordable in most resource-limited settings.MethodsA cross-sectional study of 496 Ugandans established on ART was performed at the Infectious Diseases Institute, Kampala, Uganda. Adherence, clinical and laboratory parameters were assessed for their relationship with viral failure by multivariate logistic regression. A clinical algorithm using targeted viral load testing was constructed to identify patients for second-line ART. This algorithm was compared with the World Health Organization (WHO) guidelines, which use clinical and immunological criteria to identify failure in the absence of viral load testing.ResultsForty-nine (10%) had a viral load of >400 copies/mL and 39 (8%) had a viral load of >1000 copies/mL. An algorithm combining adherence failure (interruption >2 days) and CD4 failure (30% fall from peak) had a sensitivity of 67% for a viral load of >1000 copies/mL, a specificity of 82%, and identified 22% of patients for viral load testing. Sensitivity of the WHO-based algorithm was 31%, specificity was 87%, and would result in 14% of those with viral suppression (<400 copies/mL) being switched inappropriately to second-line ART.ConclusionAlgorithms using adherence, clinical and CD4 criteria may better allocate viral load testing, reduce the number of patients continued on failing ART, and limit the development of resistance.