Latent tuberculosis infection screening of adult close contacts: a cost-utility analysis

Background The 2016 National Institute for Health and Care Excellence guidelines recommended the tuberculin skin test (TST), at a 5-mm induration size cut-off, for the diagnosis of latent tuberculosis infection (LTBI) among adult close contacts of active tuberculosis (TB) cases. This study analysed a well-characterised cohort of adult close contacts in London and assessed the cost-effectiveness of LTBI screening strategies with combinations of TST and interferon-γ release assays (IGRAs) in a decision-analytic model. Methods Close contacts of pulmonary TB cases who were tested with TST and IGRA between January 2008 and December 2010 were retrospectively reviewed. Using an NHS perspective and lifetime horizon, a decision-analytic Markov model was used to compare costs and quality-adjusted life-years (QALYs) associated with five screening strategies followed by LTBI treatment: 1) TST alone; 2) QuantiFERON-TB Gold In-Tube (QFT) alone; 3) T-SPOT.TB (T-SPOT) alone; 4) TST positive followed by QFT; 5) TST positive followed by T-SPOT. Results This study included 381 asymptomatic close contacts aged 18 to 65 years (mean±sd 35.2±11.3). 75.3% had received BCG vaccination. Among the five strategies, for a willingness-to-pay threshold of GBP 25 000 and using incremental net monetary benefit (INMB) with TST as comparator, the IGRA-alone strategies were the most cost-effective, marginally QFT over T-SPOT (QFT: GBP 214; T-SPOT: GBP 199). Conclusion Single-step IGRA, particularly QuantiFERON, is preferable for LTBI screening of adult close contacts of pulmonary TB cases.