Levels of adherence to contemporary antiretroviral regimens and the likelihood of viral suppression: a cohort study in a Brazilian metropolis

Levels of adherence to antiretroviral therapy (ART) can affect the likelihood of viral suppression differentially among ART regimens. In this prospective cohort conducted in Belo Horizonte, Brazil, we included 354 individuals who initiated ART containing tenofovir disoproxil fumarate/lamivudine/efavirenz in fixed-dose combination (TDF/3TC/EFV) or tenofovir disoproxil fumarate/lamivudine associated with dolutegravir (TDF/3TC + DTG). Viral suppression (viral load <50 copies/mL) was evaluated within six months of follow-up at different adherence levels and by therapeutic regimen. Adherence was measured by the Proportion of Days Covered (PDC) and classified into low (<= 84%), intermediate (85-89%) or high (>= 90%). The association between viral suppression, adherence levels, and other explanatory variables was analyzed using chi-square and multivariable logistic regression. Viral suppression was achieved by 76.0% of individuals and was more frequent among those who achieved higher levels of adherence (high adherence: 79.3%, intermediate: 71.4% and low: 45.2%), those on TDF/3TC + DTG, and those who had viral load <= 100,000 copies/mL at the onset of treatment (p <0.05). Moreover, individuals on TDF/3TC + DTG had an approximately 90% probability of achieving viral suppression at intermediate adherence levels. These results add new insights on the possibility of lower adherence levels for contemporary antiretroviral regimens currently used as first-line therapy worldwide.