An evaluation of the use of a negative interferon-c release assay for tuberculosis screening before TNF antagonist therapy

Tumour necrosis factor (TNF)-a antagonists, such as infliximab, adalimumab and etanercept, are widely used to treat immune-mediated inflammatory diseases. These drugs increase the risk of latent infection with Mycobacterium tuberculosis (LTBI) reactivation [1, 2]. Tuberculosis (TB) preventative chemotherapy significantly reduces this risk (74%); hence, in the UK, patients are screened for LTBI before starting TNF antagonist therapy [3]. The optimum screening strategy remains unclear. Strategies include combinations of clinical risk stratification data, T-cell interferon-c release assay (IGRA) tests and tuberculin skin tests (TSTs) [2, 4, 5]. These tests have limitations, and have discordant results when compared [6].