The effect of systematic screening of the general population on TB case notification rates

BACKGROUND: Understanding how TB case notification rates (TB-CNR) change with TB screening and their association with underlying TB incidence/prevalence could inform how they are best used to monitor screening impact. METHODS: We undertook a systematic review to identify articles published between 1 January 1980 and 13 April 2020 on TB-CNR trends associated with TB screening in the general-population. Using a simple compartmental TB transmission model, we modelled TB-CNRs, incidence and prevalence dynamics during 5 years of screening. RESULTS: Of 27,282 articles, seven before/after studies were eligible. Two involved population-wide screening, while five used targeted screening. The data suggest screening was associated with initial increases in TBCNRs. Increases were greatest with population-wide screening, where screening identified a large proportion of notified people with TB. Only one study reported on sustained screening; TB-CNR trends were compatible with model simulations. Model simulations always showed a peak in TB-CNRs with screening. Following the peak, TBCNRs declined but were typically sustained above baseline during the intervention. Incidence and prevalence decreased during the intervention; the relative decline in incidence was smaller than the decline in prevalence. CONCLUSIONS: Published data on TB-CNR trends with TB screening are limited. These data are needed to identify generalisable patterns and enable method development for inferring underlying TB incidence/ prevalence from TB-CNR trends.