Impact of active case finding for tuberculosis with mass chest X-ray screening in Glasgow, Scotland, 1950-1963: an epidemiological analysis of historical data
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Background
Community active case finding for tuberculosis was widely implemented in Europe and North America between 1940-1970, when incidence was comparable to many present-day high-burden countries. Using an interrupted time series analysis, we analysed the effect of the 1957 Glasgow mass chest X-ray campaign to inform contemporary approaches to screening.
Methods and findings
Case notifications for 1950-1963 were extracted from public health records and linked to demographic data. We fitted Bayesian multilevel regression models to estimate annual relative case notification rates (CNR) during and after a mass screening intervention implemented over five weeks in 1957 compared to the counterfactual scenario where the intervention had not occurred. We additionally estimated case detection ratios and incidence. From 11/3/1957-12/4/1957, 714,915 people (622,349 of 819,301 [76.0%] resident adults ≥15 years) were screened with miniature chest X-ray; 2,369 (0.4%) were diagnosed with tuberculosis. Pre-intervention (1950-1956), pulmonary CNRs were declining at 2.3% per year from a CNR of 222/100,000 in 1950. With the intervention in 1957, there was a doubling in the pulmonary CNR (RR: 1.95, 95% uncertainty interval [UI]: 1.80-2.11), and 36% decline in the year after (RR: 0.64, 95%UI: 0.59-0.71). Post-intervention (1958-1963) annual rates of decline (5.4% per year) were greater (RR: 0.77, 95%UI: 0.69-0.85), and there were an estimated 4,656 (95%UI: 3,670-5,725) pulmonary case notifications averted due to the intervention. Effects were consistent across all city wards and notifications declined substantially in young children (0-5 years) with the intervention.
Conclusions
A single, rapid round of mass screening with chest X-ray (probably the largest ever conducted) resulted in a major and sustained reduction in tuberculosis case notifications. Contemporary high-burden settings may achieve similar benefits with high-intensity screening.
