Background: Achieving optimal adherence to highly active antiretroviral therapy (HAART) is necessary to attain viral suppression and hence optimal clinical outcome. Interruptions in antiretroviral therapy medication often occur, but a substantial proportion restart treatment. Long-term care engagement practices and clinical outcomes have not been described among cohorts of individuals on HAART in Ethiopia. Methods: In this study we describe treatment interruption patterns over time among clients who interrupt and subsequently resume HAART, and those who are continuously engaged in treatment, and determine clinical factors associated with loss to engagement. An observational, longitudinal, retrospective cohort design was engaged, using secondary treatment program data. We analyzed differences in treatment interruption among clients who were continuously active and those that interrupted and restarted treatment at months 6, 12, 18, and 24. Cox proportional hazards regression analysis was used to identify predictors of loss from treatment. We estimated time to first treatment interruption, time to restarting after interruption, and time to second interruption. Data from all clients registered to receive HAART in ten study health facilities, from 2005 to 2014, were used to study clinical and treatment outcomes up to 60 months or study end. Results: In this study, 39% (8,759/22,647) of clients interrupted treatment for more than 1 month at least at one point during follow-up. Of these, only 35% ever restarted treatment. At the end of follow-up, the hazard of unfavorable treatment outcome (dead, lost, stopped HAART) for clients who restarted treatment at months 6, 12, 18 and 24 was higher by a factor of 1.9, 2.4, 2.6 and 2.4, as compared to those who never discontinued treatment at those times. Conclusion: HAART treatment interruption was common in the study population. In those with a history of treatment interruption, long term clinical outcomes were found to be suboptimal. Targeted interventions are required to address follow-up challenges and prevent treatment interruption.
