Cost effectiveness of different scenarios for diagnosing and treatment of LTBI of immigrant close contacts in the Netherlands

Background A possible method to reduce tuberculosis (TB) in low incidence countries is screening close contacts for latent tuberculosis infection (LTBI) and offer them preventive treatment. Tools for the screening of LTBI are tuberculin skin test (TST) and the interferon gamma release assays (IGRA) T-SPOT.TB and QuantiFERON-TB Gold in tube (QFT-GIT). It is unclear whether screening contacts with TST and/or IGRA is cost-effective in a population of immigrants. Aim The aim of this paper is to assess the cost-effectiveness of TST, T-SPOT.TB, and QFT-GIT for the diagnosis and treatment of LTBI in immigrant close contacts. Method Data for this cost effectiveness study (CEA) are mostly based on the prospective cohort study, PREDICT, expert interviews and literature. A decision tree was developed for the calculation of the average costs of 6 scenarios. The cost effectiveness is defined as the costs (in Euros) per prevented TB case and costs per quality-adjusted life years (QALY) gained. Results To prevent one TB case during the first 2 years after LTBI screening, screening with TST costs €3,709 in comparison with disease screening only, which is current practice. For the other scenarios the costs to prevent one TB case compared to disease screening only were for QFT-GIT €4217, for TSPOT.TB €16,285, for TST in combination with QFT-GIT €5,046 and for TST in combination with TSPOT.TB €17,741. If cost-effectiveness was expressed in euro per QALY gained, screening for LTBI with TST was most cost effective with €8,242 per QALY and lowest cost effective was TST in combination with TSPOT.TB, €39,424 per QALY Conclusion The data presented suggest that TST is cost-effective for LTBI screening of immigrant contacts of TB patients in the Netherlands. PREDICT is one of the first studies to investigate the PPV and NPV of QFT-GIT and T-SPOT.TB among immigrants. Also further research should investigate whether diagnosing and treatment of LTBI is cost effective if a longer period is taken into account.