Active screening for asymptomatic versus symptomatic tuberculosis in high-risk groups in a low-prevalence country: a retrospective study.

introductionAsymptomatic Tuberculosis (TB) represents up to 60% of cases in endemic countries, remains largely underdiagnosed and sustains transmission. Several European low-TB prevalence countries have implemented active screening in at-risk populations for identification of such cases. This study aims to describe clinical characteristics and possible risk factors of asymptomatic vs. symptomatic pulmonary TB cases in this setting.

methodsThis retrospective cohort study included pulmonary TB cases detected through active screening of at-risk populations at two Italian regional reference centers between 2015 and 2024. Asymptomatic and symptomatic cases were identified and compared.

resultsAmong 372 TB cases included, 56.5% belonged to the asymptomatic and 43.5% to the symptomatic group. Individuals from the first group required more often radiologic investigation with chest CT scan (145 [69%] vs. 78 [48.1%], p < 0.001). Cavitations were observed in both groups (75 [20%]); microbiologic confirmation by sputum culture, molecular methods or smear microscopy was more common in symptomatic patients (101 [75.9%] vs. 94 [63.1%], p = 0.02). Non-native individuals were more often symptomatic, younger, had history of previous TB and were more often screened due to exposure to congregate settings. Bivariate models showed that patient origin, previous TB disease history, chest CT scan and negative microbiology were associated with asymptomatic presentation, which was partly confirmed in multivariate models. DISCUSSION: Active screening in at-risk populations is essential to identify asymptomatic TB cases, which may display markers of infectiousness and therefore drive transmission. Epidemiologic risk profiling and advanced diagnostic strategies are necessary to improve early TB detection both in high and low prevalence countries.