Effect of HIV-1 low-level viraemia during antiretroviral therapy on treatment outcomes in WHO-guided South African treatment programmes: a multicentre cohort study

Background Antiretroviral therapy (ART) that enables suppression of HIV replication has been successfully rolled out at large scale to HIV-positive patients in low-income and middle-income countries. WHO guidelines for these regions define failure of ART with a lenient threshold of viraemia (HIV RNA viral load >= 1000 copies per mL). We investigated the occurrence of detectable viraemia during ART below this threshold and its effect on treatment outcomes in a large South African cohort. Methods In this observational cohort study, we included HIV-positive adults registered between Jan 1, 2007, and May 1, 2016, at 57 clinical sites in South Africa, who were receiving WHO-recommended ART regimens and viral load monitoring. Low-level viraemia was defined as the occurrence of at least one viral load measurement of 51-999 copies per mL during ART. Outcomes were WHO-defined virological failure (one or more viral load measurement of >= 1000 copies per mL) and switch to second-line ART. Risks were estimated with Cox proportional hazard models. Findings 70930 patients were included in the analysis, of whom 67644 received first-line ART, 1476 received second-line ART, and 1810 received both. Median duration of follow-up was 124 weeks (IQR 56-221) for patients on first-line ART and 101 weeks (IQR 51-178) for patients on second-line ART. Low-level viraemia occurred in 16013 (23%) of 69454 patients, with an incidence of 11.5 per 100 person-years of follow-up (95% CI 11.4-11.7), during first-line ART. Virological failure during follow-up occurred in 14?380 (22%) of 69454 patients on first-line ART. Low-level viraemia was associated with increased hazards of virological failure (hazard ratio [HR] 2.6, 95% CI 2.5-2.8; p<0.0001) and switch to second-line ART (HR 5.2, 4.4-6.1; p<0.0001]) compared with virological suppression of less than 50 copies per mL. Risk of virological failure increased further with higher ranges and persistence of low-level viraemia. Interpretation In this large cohort, low-level viraemia occurred frequently and increased the risk of virological failure and switch to second-line ART. Strategies for management of low-level viraemia need to be incorporated into WHO guidelines to meet UNAIDS-defined targets aimed at halting the global HIV epidemic.