Latent tuberculosis screening with Interferon-Gamma Release Assay alone cost-effective: Study

The study is published in the Pulmonology Journal.

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.

Therefore, Sofia Sousa and colleagues from the Public Health Unit - South Sousa Valley, Northern Regional Health Administration, Paredes, Portugal carried out the present study with the aim to compare the cost-effectiveness of two-step TST/IGRA with the current IGRA-only screening strategy in immunocompetent individuals exposed to individuals with respiratory TB.

The authors reviewed clinical records of individuals exposed to infectious TB cases diagnosed, in two TB outpatient centers. They 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.

The incremental cost-effectiveness ratio (ICER) was calcuated 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. Adjusted odds-ratios was also calculated to test the association between diagnosis of LTBI and screening strategy and estimated the total cost for averting a potential TB case.

The following results were found out-

2. IGRA-only strategy yielded a higher screening effectiveness for diagnosing latent tuberculosis infection (aOR 2.12, 95%CI: 1.53 - 2.94).
3. ICER was €106 per LTBI diagnosis, representing increased effectiveness with a slightly increased cost of IGRA-only screening strategy.

Hence, the authors concluded that "screening with IGRA-only is more cost-effective than the two-step TST/IGRA testing strategy, preventing a higher number of cases of TB cases."