Long-term adherence to first-line highly active antiretroviral therapy in a hospital-based cohort: predictors and impact on virologic response and relapse

A high level of adherence to highly active antiretroviral therapy (HAART) is essential to minimize the risk of treatment failure and HIV disease progression. This cohort study evaluated the prevalence and predictors of long-term adherence with first-line HAART in a hospital-based unselected sample of HIV patients from central Italy, and examined the association between adherence and virological response or relapse. Between July 1996 and June 2004, 171 patients (67.3% males; mean age, 41.2 years) were followed for at least 24 weeks and up to 8 years. Adherence was measured by patient self-reports and confirmed using pharmacy records. The prevalence of high-level adherence (>or=90%) at 6 months was 88.3%; slightly less than 80% at 12 months. The incidence of adherence failure in the sample remained fairly stable until 24 months of follow-up, then it declined about 5% every 6 months. Cox analysis showed that compared to single/separated patients, homeless and married persons were, respectively, 1.95 times more likely and two times less likely to experience adherence failure (p < 0.05). The adjusted risk of adherence failure among patients who did not suffer drug-related toxicity was 0.57 (p < 0.05). Medication adherence was significantly associated with shorter time to virological response and longer time to relapse. Adherents were 1.69 times more likely to achieve viral suppression and nine times less likely to experience relapse than nonadherents (p < 0.01). Efforts at improving adherence should be prolonged for at least 24 months. A protective role of marriage for adherence failure is promising but requires confirmation in further research, that should also clarify the exact mechanisms determining the association.