Survival of people with untreated tuberculosis: effects of time, geography and setting

Background An estimated 40% of people who developed tuberculosis in 2021 were not diagnosed or treated. Pre-chemotherapy era data are a rich resource for learning more about survival for people with untreated TB. We aimed to identify heterogeneities in these data to inform more precise use of these estimates. Methods We extracted survival data from pre-chemotherapy era papers reporting TB specific mortality and/or natural recovery data. We used Bayesian parametric survival analysis to model the survival distribution. We stratify our results by geography (North America versus Europe), time (pre-1930 versus post-1930), and setting (sanitoria versus non-sanitoria). We also estimated the baseline disease severity stratified by those treated in sanitoria and those not. Results We found 12 studies with TB-specific mortality data. Ten-year survival was an estimated 69% in North America (95 CI: 54%-81%) and 36% in Europe (95% CI: 10%-71%). Only 38% (95% CI: 18%-63%) of non-sanitorium individuals survived to 10 years compared to 69% (95% CI: 41%-87%) of sanitoria/hospitalized patients. Disease severity at baseline differed significantly between sanatorium and non-sanatorium studies (22.0% versus 43.0% for far advanced disease; 61.8% versus 35.4% for moderately advanced disease). There were no significant differences between people diagnosed pre-1930 and post-1930 (5 year survival pre-1930: 0.65; 95% CI: 0.44-0.88 versus post-1930: 0.72; 95% CI: 0.41-0.94). Conclusions Mortality and natural recovery risks vary substantially by location and setting. These heterogeneities need to be considered when using pre-chemotherapy data to make inferences about expected survival of people with undiagnosed TB.