Comparison of active tuberculosis case finding strategies for immigrants in South Korea: Epidemiology and cost-effectiveness analysis

BACKGROUND: Tuberculosis (TB) is one of the serious infectious diseases in South Korea, with 49 new cases per 100,000 people and 629 multi-drug resistant (MDR) cases reported in 2020. TB is increasing among immigrants in S. Korea, and various TB case finding strategies are being performed for screening. We compared active case finding (ACF) with passive case finding (semi-PCF) across epidemiological characteristics and investigated a cost-effective strategy for screening immigrants for TB. METHODS: ACF driven by non-governmental organizations and semi-PCF as part of the government’s visa renewal process using CXR with additional acid-fast bacilli (AFB) smear and cultures were performed. Epidemiological parameters were compared between the two TB screening projects, and costs were collected. Cost-effectiveness was evaluated using a decision analysis model from the health system perspective. The primary outcome was incremental cost-effectiveness ratio (ICER) per averted TB case. Additional probabilistic sensitivity analysis was conducted. RESULTS: ACF (2.02%) showed a higher TB prevalence rate than semi-PCF (0.67%) on CXR. For subjects older than 60 years, the suspected TB rate on CXR was significantly higher in ACF (36.6%) than in semi-PCF (12.2%) (P<0.01). TB incidence among the family visa type was significantly higher in ACF (1.96%) than in semi-PCF (0.88%) (P < 0.0012). Costs for ACF ($666.92) were $20.784 higher than for semi-PCF ($646.13), but TB progression decreased by 0.02, resulting in an ICER of $948.18 per averted TB case. In sensitivity analysis, the indirect costs of ACF and semi-PCF had the highest impact on ICER. CONCLUSION: ACF found more TB cases than semi-PCF through CXR screening, and suspect cases with old age and family visa type were more common in ACF than in semi-PCF. ACF is cost-effective as a TB screening strategy for immigrants.