Comparing the cost-effectiveness of two screening strategies for latent tuberculosis infection in Portugal

Introduction and objectives: Screening for latent tuberculosis infection (LTBI) in close contacts of infectious TB cases might include Tuberculin Skin Test (TST) and Interferon-Gamma Release Assays (IGRA), in combination or as single-tests. In Portugal, the screening strategy changed from TST followed by IGRA to IGRA-only testing in 2016. Our objective was to compare the costeffectiveness of two-step TST/IGRA with the current IGRA-only screening strategy in immunocompetent individuals exposed to individuals with respiratory TB. Materials and Methods: We reviewed clinical records of individuals exposed to infectious TB cases diagnosed in 2015 and 2016, in two TB outpatient centers in the district of Porto. We estimated medical, non-medical and indirect costs for each screening strategy, taking into account costs of tests and health care personnel, travel distance from place of residence to screening site and employment status. We calculated the incremental cost-effectiveness ratio (ICER) as the cost difference between the two screening strategies with the difference number of LTBI diagnosis as a measure of cost-effectiveness, assuming that treating LTBI is a cost-effective intervention. We also calculated adjusted odds-ratios to test the association between diagnosis of LTBI , screening strategy and estimated the total cost for averting a potential TB case. Results: We compared 499 contacts TST/IGRA screened with 547 IGRA-only. IGRA-only strategy yielded a higher screening effectiveness for diagnosing latent tuberculosis infection (aOR 2.12, 95%CI: 1.53 -2.94). ICER was euro 106 per LTBI diagnosis, representing increased effectiveness with a slightly increased cost of IGRA-only screening strategy. Conclusions: Our data suggests that in Portugal LTBI screening with IGRA-only is more cost-effec-tive than the two-step TST/IGRA testing strategy, preventing a higher number of cases of TB cases. (c) 2021 Sociedade Portuguesa de Pneumologia. Published by Elsevier Espana, S.L.U. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).