Viremia, resuppression, and time to resistance in human immunodeficiency virus (HIV) subtype C during first-line antiretroviral therapy in South Africa

Background. Episodes of viremia are common in African antiretroviral therapy (ART) programs. We sought to describe viremia, resuppression, and accumulation of resistance during first-line combination ART (cART) in South Africa. Methods. Retrospective analysis of a cohort receiving zidovudine, lamivudine, and either efavirenz or nevirapine with human immunodeficiency virus (HIV) RNA monitoring every 6 months. We assessed viremia (HIV RNA >1000 copies/mL after initial HIV RNA response) and resuppression (HIV RNA <400 copies/mL after viremia). Genotypic resistance testing was performed using stored plasma on a subset of patients at first detection of viremia and subsequently among patients with persistent viremia. Results. Between 2002 and 2006, 3727 patients initiated cART (median CD4, 147 cells/mm³). Of 1007 patients who developed viremia, 815 had subsequent HIV RNA assays, and 331 (41%) of these resuppressed without regimen switch. At identification of viremia, 45 (66%) of 68 patients had HIV-1 drug resistance, 42 (62%) had nonnucleoside reverse-transcriptase inhibitor (NNRTI)-resistance, 25 (37%) had M184V/I, and 4 (6%) had multinucleoside analogue drug mutations. By 12 months of persistent viremia among a subset of 14 patients with resistance testing to 12 months, 11 (78%) had nonnucleoside reverse-transcriptase inhibitor (NNRTI)-resistance, 8 (57%) had M184V/I, and 2 (14%) had multi-nucleoside analogue drug mutations. Resistance was associated with a reduced probability of resuppression; however, 50% of patients with NNRTI resistance resuppressed while receiving an NNRTI. Conclusions. The majority of patients had NNRTI resistance mutations at detection of viremia. However, 41% resuppressed without regimen switch. Our findings support maximizing first-line use while minimizing risk of significant cross-resistance by implementing intensive adherence support and repeat HIV RNA testing 3-6 months after detecting viremia, with regimen switch only if viremia persists.