Impact of active case finding for tuberculosis with mass chest X-ray screening in Glasgow, Scotland, 1950–1963: An epidemiological analysis of historical data.

Background: Community active case finding (ACF) for tuberculosis was widely implemented in Europe and North America between 1940 and 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 to 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 (CNRs) during and after a mass screening intervention implemented over 5 weeks in 1957 compared to the counterfactual scenario where the intervention had not occurred. We additionally estimated case detection ratios and incidence. From 11 March 1957 to 12 April 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 to 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] [1.81, 2.11]) and 35% decline in the year after (RR: 0.65, 95% UI [0.59, 0.71]). Post-intervention (1958 to 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 4,599 (95% UI [3,641, 5,683]) pulmonary case notifications averted due to the intervention. Effects were consistent across all city wards and notifications declined in young children (0 to 5 years) with the intervention. Limitations include the lack of data in historical reports on microbiological testing for tuberculosis, and uncertainty in contributory effects of other contemporaneous interventions including slum clearances, introduction of BCG vaccination programmes, and the ending of postwar food rationing. Conclusions: A single, rapid round of mass screening with chest X-ray (probably the largest ever conducted) likely resulted in a major and sustained reduction in tuberculosis case notifications. Synthesis of evidence from other historical tuberculosis screening programmes is needed to confirm findings from Glasgow and to provide insights into ongoing efforts to successfully implement ACF interventions in today's high tuberculosis burden countries and with new screening tools and technologies. Peter MacPherson and colleagues analyze public health records and demographics data using an interrupted time series approach to explore the effect of the 1957 Glasgow mass chest X-ray campaign for tuberculosis case finding. Author summary: Why was this study done?: Tuberculosis screening is conditionally recommended by the World Health Organization for populations with a high prevalence of disease or other structural risk factors. There is considerable uncertainty over the optimal approaches and population impact of tuberculosis screening. Between 1930 and 1970, mass screening for tuberculosis was widely undertaken, in Europe and North America, but there has been little attempt to understand what effect these programmes had on the trajectory of tuberculosis epidemics. What did the researchers do and find?: Over a 5-week period, in 1957, the city of Glasgow, Scotland implemented a tuberculosis screening programme comprising mass miniature X-ray of around 715,000 people supported by community mobilisation. Tuberculosis notification data and population demographics were extracted from city Medical Officer of Health reports between 1950 and 1963, and multilevel interrupted time series regression models were constructed to investigate the effect of the mass screening campaign on tuberculosis notifications, compared to the counterfactual scenario where the intervention had not occurred. Before the mass screening intervention (1950 to 1956), tuberculosis notification rates were declining at 2.3% per year, and rates doubled in the year of the intervention (1957). Post-intervention, tuberculosis notification rates declined at 5.4% per year, and there were an estimated 4,599 pulmonary notifications averted. Intervention effects were consistent across all 37 city wards, but showed differing effects by age group and sex. What do these findings mean?: A single, rapid, and high coverage round of mass tuberculosis screening, supported by intensive community mobilisation, likely had a major impact on changing the tuberculosis epidemiology trajectory in Glasgow. Greater understanding of how improved housing, social conditions, and tuberculosis care and prevention contributed to this screening effect is needed. Synthesis of evidence from other historical tuberculosis screening programmes is needed to confirm findings from Glasgow, and to support efforts to successfully implement active case finding (ACF) interventions in today's high tuberculosis burden countries and with new screening tools and technologies. [ABSTRACT FROM AUTHOR]