Impact of definitions of loss to follow-up (LTFU) in antiretroviral therapy program evaluation: variation in the definition can have an appreciable impact on estimated proportions of LTFU

Variation in the definitions of LTFU within cohort analyses can have an appreciable impact on estimated proportions of LTFU over 2 years of follow-up. Use of a standardized definition of LTFU is needed to accurately measure program effectiveness and comparability between programs.