Evaluating surveillance definitions of HIV viral suppression 2015-2019: Which definition best detected barriers to care?

Background: People living with HIV (PLWH) who have not achieved or maintained viral suppression post-diagnosis likely face multiple barriers to HIV care. To identify these barriers a universally accepted definition of viral suppression is needed. The most common definition, the Center for Disease Control and Prevention (CDC) definition, contains simplifying assumptions that may misclassify individuals and attenuate associations. In this study, we evaluated alternative definitions of viral suppression on their ability to identify barriers to care. Design and methods: We used HIV surveillance data to classify participants of the 2015-2019 Washington Medical Monitoring Project (MMP) as virally suppressed or not using the CDC definition and two definitions that assess viral suppression over a longer period ("Enriched" and "Durable"). We identified barriers to suppression from literature (unstable housing, illicit drug use, poor mental health, heavy drinking, recent incarceration, racism, and poverty) and measured them using interview questions from MMP. We compared the rate ratios (RR) of being not virally suppressed using each definition for each barrier. Results: There were 858 PLWH in our study. All viral suppression definitions classified a similar proportion of people as suppressed (85%-89%). The durable viral suppression definition consistently yielded the largest rate ratios (e.g. unstable housing: CDC RR = 1.3, 95% CI 0.9-1.8; Enriched 1.5, 95% CI 1.0-2.2; Durable 2.2, 95% CI 1.6-3.1) and reclassified 10% of the population relative to the CDC definition. Conclusions: Longitudinal definitions for viral suppression may yield less misclassification and serve as superior tools for identifying and curtailing barriers to HIV care.