Abstract
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 assess the cost-effectiveness of LTBI screening strategies with combinations of TST and interferon-gamma 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 a 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: TST alone, IGRA (QuantiFERON-TB Gold In-Tube [QFT] or T-SPOT.TB [T-SPOT]) alone, and TST positive followed by IGRA.
Results
This study included 381 asymptomatic close contacts aged 18 to 65?years (mean 35.2 (sd: 11.3)). 75.3% had received BCG vaccination. Among the five strategies, for a willingness to pay threshold of £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 £214; T-SPOT £199).
Conclusion
Single-step IGRA, particularly QuantiFERON, is preferable for LTBI screening of adult close contacts of pulmonary TB cases.
