Background and objectivesAdherence to antiretroviral treatment is a key challenge for paediatric HIV care. Among children and adolescents living with HIV, lower levels of adherence have been reported compared to adults. Individual, caregiver-, health services-related and sociocultural factors were shown to impact on these outcomes. Study objectives were to assess adherence in a paediatric population in rural Tanzania comparing two measurement methods, and to investigate the association between virologic suppression and demographic, clinical, drug- and family-related factors.MethodsThis cross-sectional study was conducted among children and adolescents enrolled in Bukumbi HIV Care and Treatment Clinic (Misungwi district, Mwanza region) in the north of Tanzania, where the HIV prevalence is 7.2%. Adherence was measured through viral load and pill count. Kappa statistics assessed the level of agreement between the methods; bivariate and multivariable analyses identified factors independently associated with virologic suppression.ResultsN = 72 participants (n = 49 children; n = 23 adolescents) with a median age of eight years were enrolled. 62.5% and 65.3% of the individuals presented an optimal adherence according to viral load and pill count respectively, but among 40% viral load results diverged from the pill count method. In multivariable analysis, living outside Misungwi district and having CD4 counts above 500/μl were significantly associated with optimal adherence.ConclusionChildren and adolescents living with HIV in Mwanza show high rates of suboptimal adherence. The poor agreement between pill count and viral load results raises concerns about the interpretation of these measurements in clinical practice.