METHODS: We used data collected from 21 adult and 17 pediatric sites (across 13 and 6 countries/territories, respectively) in the International Epidemiology Databases to Evaluate AIDS - Asia-Pacific cohort. ART failure was defined as viral, immune, or clinical consistent with WHO guidelines.

RESULTS: A total of 8567 adults and 6149 children contributed data. Frequency of CD4 count monitoring declined between 2010 and 2019 among adult sites (from 1.93 to 1.06 tests/person per year, a 45.1% decline) and pediatric sites (from 2.16 to 0.86 testsperson per year, a 60.2% decline), whereas rates of viral load monitoring remained relatively stable. The proportion of adult and pediatric treatment failure detected as immune failure declined (from 73.4% to 50.0% and from 45.8% to 23.1%, respectively), whereas the proportion of failure detected as viral failure increased (from 7.8% to 25.0% and from 45.8% to 76.9%, respectively). The proportion of ART failure detected as clinical failure remained stable among adult and pediatric sites. The largest shifts in ART monitoring and failure type occurred in lower middle-income countries.