Cost-effectiveness of M. tuberculosis specific Interferon-gamma release assay testing for the treatment of latent tuberculosis infection in Switzerland

Objectives: To assess the cost-effectiveness of the new T-SPOT ® . TB assay versus the Tuberculin Skin Test (TST) for screening contacts for latent tuberculosis (LTBI) in Switzerland. Methods: Health and economic outcomes of isoniazid (INH) treatment of 20- and 40-year-old close contacts were compared in a Markov model over a 20-year period following screening with TST only (at three cut-off values), T-SPOT. TB alone or in combination with the TST. Results : T-SPOT. TB based treatment was cost-effective at €11,621 per life-year-gained (LYG) in the younger and €23,691/LYG in the higher age group. No TST-based programs were cost-effective, except at a 15mm-cut-off in the younger group only where the cost-effectiveness (€26,451/LYG) just fell below the willingness-to-pay threshold. Combination of the TST with T-SPOT. TB slightly reduced the total cost compared with the T-SPOT. TB alone by 4.4% and 5.0% in the younger and older groups respectively. The number of contacts treated to avoid one case of tuberculosis decreased from 50 [95% CI 32–106] with the TST (10mm cutoff) to 18 [95% CI 11–43] if T-SPOT. TB was used. Conclusions : Using T-SPOT. TB alone or in combination with the TST for screening of close contacts before LTBI treatment is highly cost-effective in reducing the disease burden of TB.