Impact of different patterns of nonadherence on the outcome of highly active antiretroviral therapy in patients with long-term follow-up

Objectives: The aim of the study was to evaluate the impact of different patterns of nonadherence on treatment outcomes in patients with long-term follow-up. Methods: This cohort study included patients who began highly active antiretroviral therapy during 1996-1999, with the last follow-up in 2007. Adherence was evaluated every 2 months by monitoring of pharmacy refills and by using self-reports. Patients were considered nonadherent at a specific visit when less than 90% of the prescribed drugs had been taken. Adherence was categorized as follows. (A) Continuous adherence: a patient had to be adherent in all of the evaluations throughout the period of follow-up. (B) Treatment interruption: drugs were not taken for more than 3 days, for any reason. Treatment failure was defined as viral load > 500 HIV-1 RNA copies/mL or death. Cox proportional risk models were used to calculate adjusted relative hazards (ARHs) of treatment failure. Results: A total of 540 patients were included in the study, with a median follow-up of 8.3 years. Only 32.78% of patients achieved and maintained continuous adherence, and 42.78% of patients had treatment interruptions. Noncontinuous adherence [ARH 1.48; 95% confidence interval (CI) 1.02-2.14] and treatment interruptions (ARH 1.39; 95% CI 1.04-1.85) were associated with treatment failure for the overall cohort; however, for patients with more than 3 years of follow-up, only treatment interruptions were independently associated with treatment failure. Conclusions: Only one-third of patients managed to achieve continuous adherence, and almost half of the patients had treatment interruptions, which have a particularly marked effect on treatment outcomes over the long term.