Clinical applicability of T-cell interferon-a release assay for tumour necrosis factor-a inhibitor therapy in severe psoriasis.

Many studies have found that screening and treatment of latent tuberculosis (TB) before starting treatment with tumour necrosis factor (TNF)-a inhibitors reduces associated TB infections. The new T-cell interferon-a release assay (TIGRA), is more specific and sensitive for detection of latent TB compared with the tuberculin skin test (TST). We report results of TIGRA in our first 63 patients commencing TNF-a inhibitors for severe psoriasis. Of the 63 patients, 5 (7.9%) had a positive TIGRA result and were started on treatment for latent TB. We found that the only risk factor for TB associated with a positive TIGRA was a history of travel to countries with high TB incidence. To our knowledge, this is the first study to identify the background risk (7.9%) of latent TB in an endemic UK population. This result emphasizes the importance of TIGRA testing to reduce the risk of TB in patients treated with TNF-a inhibitor.