Incidence and Factors Associated with HIV Virologic Failure among Adults Undergoing First-Line Antiretroviral Therapy: a Five-Year Retrospective Study in Thailand

Virologic failure and HIV drug resistance have emerged with the widespread use of antiretroviral therapy (ART). An understanding of these predictors is the basis for prevention strategies to achieve a high treatment success rate. A retrospective cohort study was conducted among antiretroviral-naïve people living with HIV (PLWH) registered in the national AIDS program database of the National Health Security Office Region 4, Thailand, between January 2014 and December 2018. To determine the cumulative incidence rate of virologic failure and related factors, all PLWH were monitored for viral load status through December 2019. Virologic failure was defined as HIV viral load >1,000 copies/mL after 6 months of ART. Of the 42,229 PLWH identified, 10,211 PLWH with primary ART regimens and follow-up data were included. There were 67.1% males, and the mean age was 35 years (standard deviation: 11.6 years). During the median observation period of 0.88 years (interquartile range: 0.23-1.94 years) after ART initiation, 2.4% (242/10,211) of the PLWH experienced virologic failure. The Cox proportional hazard model revealed that the risk of developing virologic failure was significantly associated with age <30 years and baseline CD4 cell count ≤200 cells/mm³ . Active case finding, early ART initiation, and strengthening of the HIV continuum of care intervention are strongly recommended in order to minimize treatment failure.