Generalisability, strengths, and limitations
TB
The TREATS TB prevalence survey was large, including around 50,000 individuals, and covering 21 communities. Nevertheless, the study was only powered to detect fairly large reductions (of the order of 40% to 50%) in TB prevalence in the PopART intervention trial arms (arms A and B) compared with the standard-of-care arm, and also the between-community variation in TB prevalence was larger than had been anticipated. Also, the HPTN 071 (PopART) study was designed to be balanced across trial arms on pre-trial HIV prevalence, but not on indicators of TB burden, and for most of the South African communities information on pre-trial TB prevalence was not available. The proportion of individuals who participated in the survey, among all who were invited to participate, was around 5% higher in arms A and B combined compared with arm C, but the age-sex distribution and HIV prevalence among participants was similar across the trial arms, showing that the trial had good balance across trial arms on these key individual characteristics. The missing data on prevalent TB status introduced additional uncertainty to our prevalence estimates and trial arm comparisons, but imputation of missing data was done to limit bias and sensitivity analyses showed that our findings were robust to different assumptions. Lastly, the CHiPs were a similar cadre of staff as could be employed programmatically, so our study provides evidence about the effectiveness of the PopART intervention in reducing TB prevalence in close-to-programmatic conditions.