Does switching from multiple to single-tablet regimen containing the same antiretroviral drugs improve adherence? A group-based trajectory modeling analysis.

Combination Antiretroviral Therapy (cART) in single-tablet regimens (STR) is a simplification strategy that can potentially improve medication adherence and clinical outcomes. We conducted a retrospective cohort study of 1206 patients using efavirenz, tenofovir and lamivudine in multiple-tablet regimen who switched to the STR containing the same active ingredients in a southeast metropolis in Brazil. We measured adherence using the proportion of days covered (PDC≥95%) and evaluated this outcome before and after the switch using paired non-parametric statistics. Additionally, we used group-based trajectory modeling to identify adherence patterns to cART for each period and evaluate the migration behavior of patients between the trajectory groups. We observed a 14% increase in the proportion of adherent patients after switching to STR and a 6.2% increase in the proportion of patients with CD4 count>500 cells/µl (p < 0.001), without changes in viral load outcomes. We identified four adherence trajectories in each period. Most patients (60%, n = 722) migrated towards a group with better adherence trajectory or remained in the trajectory group with the highest probability of adherence after the switch. Our findings suggest that the implementation of the STR had a positive impact on adherence and CD4 count. This may potentially improve virologic outcomes later on treatment.