Impact of contact investigation and tuberculosis screening among high-risk groups in Denmark

SETTING: The objective of tuberculosis (TB) screening in low-incidence countries is to identify TB patients earlier, ideally to improve health outcomes and reduce Mycobacterium tuberculosis transmission. In this retrospective study, we compare hospitalisation (morbidity) and smear positivity rates (infectiousness) in TB patients identified through active case finding (ACF) with patients identified through passive case finding (PCF). METHODS: ACF patients were identified by screening socially marginalised persons or through contact investigation. Logistic regression was used to model the associations between case-finding group (ACF/PCF) and hospitalisation, and between case-finding group and smear positivity rates. RESULTS: A total of 108 patients were identified through ACF and 332 through PCF. Thirty (27.8%) ACF patients and 153 (46.1%) PCF patients were hospitalised. In the adjusted models, ACF patients (OR 0.24, P < 0.001) and ACF subgroups identified using mobile X-ray screening, spot sputum culture screening and contact investigation were significantly less likely to be hospitalised than PCF patients. Thirty-one (34.4%) ACF patients and 127 (50.4%) PCF patients were smear positive. ACF patients (OR 0.30, P < 0.001) and ACF subgroups identified through contact investigation and spot sputum culture screening were less likely to be smear-positive than PCF patients. CONCLUSIONS: These findings suggest that ACF reduces morbidity and infectiousness among TB patients, thereby potentially improving health outcomes and reducing transmission of M. tuberculosis.