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.