Sample size and survey timing
TB
The TREATS TB prevalence survey was conducted among a random sample of individuals aged ≥15 years during 2019 to 2021. The target sample size was 3,000 to 4,000 participants in each arm C community and 1,500 to 2,000 participants in each arm A and arm B community, with a total targeted sample size of around 50,000 participants. With an average of 1,750 participants in each arm A and arm B community, an average of 3,500 participants in each arm C community, an assumed coefficient of variation k of 0.25, and an assumed 50% reduction in TB prevalence in arms A and B compared with arm C, study power was 91% if average arm C TB prevalence was 1%, and 89% if average arm C TB prevalence was 0.8%. The corresponding figures for study power to show a 45% reduction in TB prevalence were 84% and 81%, respectively. The assumption that TB prevalence could be reduced by around 50% after several years of delivery of the PopART intervention was informed by mathematical modelling projections that were done before the start of the TREATS study (see Community sensitisation was conducted prior to the start of prevalence survey activities, including distribution of information leaflets, door-to-door information provision, and involvement of the Community Advisory Board (CAB).