Background: Although treatment adherence is a major challenge in sub-Saharan Africa, it is still unknown which longitudinal patterns of adherence are the most detrimental to long-term virological response to non-nucleoside reverse transcriptase inhibitor (NNRTI) regimens. This analysis aimed to study the influence of different time patterns of adherence on virological failure after 24 months of treatment in Cameroon.
Methods: Antiretroviral therapy (ART) adherence data were collected using face-to-face questionnaires administered at months 1, 3, 6, 12, 18 and 24. Virological failure was defined as viral load >40 copies/ml at month 18 and/or 24. Two combined indicators of early adherence (months 1, 3 and 6) and adherence during the maintenance phase (months 12, 18 and 24) were designed to classify patients as always adherent during the early or maintenance phase, non-adherent at least once and having interrupted ART for >2 days at least once at any visit during either of these two phases.
Results: Virological failure occurred in 107 (42%) of the 254 patients included in the analysis. In the early and maintenance phases, 84% and 76%, respectively, were always adherent, 5% and 5% were non-adherent and 11% and 20% experienced ≥ 1 treatment interruption. Early non-adherence was independently associated with virological failure (adjusted OR 7.2 [95% CI 1.5, 34.6]), while only treatment interruptions had a significant impact on virological failure during the maintenance phase (adjusted OR 2.1 [95% CI 1.1, 4.4]).
Conclusions: ART NNRTI-regimens used in sub-Saharan Africa seem to 'forgive' deviations from good adherence during the maintenance phase. Optimizing adherence in the early months of treatment remains crucial, especially in a setting of poor health care infrastructure and resources.