Comparison of tuberculin skin test and interferon-gamma assays in patients with moderate to severe psoriasis who are candidates for antitumour necrosis factor-alpha therapy

Biologically based agents (biologics) are novel therapeutic options in the treatment of moderate to severe psoriasis. However, the immunosuppressive effects of biologic agents are also a reason to expect higher rates of adverse events, such as infections and malignancies. To date, reactivation of latent tuberculosis infection (LTBI) is a major complication of tumour necrosis factor (TNF)-α antagonists. Until recently, there were no alternatives to the tuberculin skin test (TST) for diagnosing LTBI. However, an alternative has now emerged in the form of a new in vitro test: the interferon (INF)-γ assays. There are at present two commercially available assays, T-SPOT.TBTM (T-SPOT) and QuantiFERON-TB Gold (QFT-G). In this study, a new version of QFT-G has been used, the QuantiFERON TB Gold ‘in tube’ (QFT-GIT), which also included the TB7.7. The aim of our study was to compare IFN-c assays with TST for detection of tuberculosis (TB) infection in patients due to start anti-TNF-a therapy.