Long term adherence to antiretroviral therapy in a South African cohort.

Abstract

Background Current treatment of HIV requires life-long antiretroviral therapy (ART) to suppress HIV replication. Adherence to medication is a critical component of treatment success, where ≥95% of doses, must be taken to achieve and maintain undetectable viral loads which are essential for successful patient and public health outcomes. Although South Africa recently introduced universal test and treat (UTT) and supports the largest number of people living with HIV (PLWH) on treatment in the world, there is limited data on long term adherence in our population. Objective The aim of this project was to retrospectively assess long term adherence in HIV infected patients on ART for at least five years or longer in order to inform long term care. Methodology Long-term adherence to ART was retrospectively analysed in HIV infected, ART naïve patients, first enrolled in a randomised controlled trial assessing tuberculosis (TB) and HIV treatment integration (N=642) and subsequently followed post-trial in an observational cohort study (N=402) in Durban, South Africa. Adherence was determined by assessing monthly or quarterly (depending on appointment schedule) pharmacy pill counts for patients on ART for five years or longer. Results From the initial randomized control trial cohort of 642 patients, 270 met the inclusion criteria for this analysis; 54.8% were female, median age was 34 years (IQR: 29-40) and median time on ART was 70 months (IQR: 64-78). Mean ART adherence was maintained at ≥ 95% for each year on ART and 93.9% of patients maintained viral suppression by the end of the follow up period. Pill count based adherence estimates showed high sensitivity (95%; 95%CI: 91-98%) in predicting viral suppression but poor specificity (9%; 95%CI: 0-41%) for predicting detectable viral loads at five years post-ART initiation. However, half of all patients had at least one sub-optimal (<95%) pill count in the first six months after ART initiation and <20% between the first and sixth year. Viral suppression was 87.4% six months after ART initiation and increased thereafter, remaining >92% throughout follow-up. HIV and TB co-treatment or switching to second line regimens with high pill burdens did not worsen adherence. Mean adherence was >99% in stable patients provided with an extended 90-day ART supply. Conclusion Our study found overall high adherence to ART in this South African cohort followed up over a period of more than five years. Treatment outcomes were successful on both first and second line treatment. Pill count was not a good predictor of virologic failure in our study and viral load measurement should be used as the benchmark for monitoring treatment response as required by current guidelines. However, adherence during the initial six months after ART initiation has been shown to impact long term treatment outcomes, therefore, pill count may be used as a quick, simple measure of adherence to identify patients with early adherence challenges and provide the opportunity for timeous adherence interventions. Optimal long-term adherence with successful treatment outcomes are possible within a structured ART programme with close adherence monitoring.This adherence support approach and these findings are relevant in the era of UTT.