Direct costs of three models for the screening of latent tuberculosis infection.

The aim of the present study was to compare the direct costs of three models for detection of latent tuberculosis infection (LTBI) in routine clinical practice in Switzerland. Comparison of the overall costs of screening for LTBI, including medical and radiological examination, and preventive treatment associated with three screening models was carried out. Model 1 relies only on the tuberculin skin test (TST) according to the current national guidelines, model 2 relies on T-SPOT.TB (Oxford Immunotec, Oxford, UK) only and model 3 relies on TST followed by confirmation of positive results by T-SPOT.TB. Costs were taken directly from the clinic's figures. Clinical assumptions were based on the 267 patients who were referred to the clinic over the study period. Model 3 was found to be the most cost-effective. Using only the skin test (model 1) was the least cost-effective. If only one test for LTBI is to be used, then model 2 (using T-SPOT.TB only) is cheaper than using the TST (model 1). Screening for latent tuberculosis infection by tuberculin skin test followed by confirmation with T-SPOT.TB is less costly than screening with tuberculin skin test alone, as it allows a reduction in the number of people who receive preventive treatment. In groups with a high proportion of negative tuberculin skin tests, screening with T-SPOT.TB test only may be the most cost-effective.