T1258 Effects of Corticosteroid Treatment on the Performance of QuantiFERON Gold in-Tube Test in the Screening of Latent Tuberculosis Infection

Introduction: Detection of Latent Tuberculosis Infections (LTBI) in patients with autoimmune diseases (e.g. Inflammatory Bowel Disease, Rheumatological Diseases) prior to treatment with anti-TNFα is mandatory because of the risk of reactivation of LTBI. Our objectives were to evaluate the effect of corticosteroids treatment on Interferon Gamma Release Assay performance and to evaluate the concordance between three tests (QuantiFERON Gold InTube (QFT-IT), Tuberculin Skin Test (TST) and Chest X-Ray). Patients and methods: As a prospective multi-center study we included a total number of 265 patients with autoimmune diseases who were potential candidates to treatment with anti-TNF-α drugs. The patients were screened for LTBI with an interview (history and risks for tuberculosis, BCG vaccination history), a Chest X-ray, a QFT-IT test and TST. Results: There was a lower median mitogen Interferon-γ response in patients treated with corticosteroids alone compared to no treatment (p < 0.001) or other treatments (p = 0.002). We also found a higher risk of an indeterminate QFT-IT in patients treated with corticosteroids (AOR = 8.7 (2.2 33.7), p = 0.0018). In total, 23% (54/238) had a positive TST, 3% (7/248) had a positive QFT-IT, 5% (12/248) had an indeterminate QFT-IT and 2% (5/236) had a TB-suspicious Chest X-rays. As expected there was a very poor concordance between the three tests. The calculated agreement for TST and QFT-IT was of 77% with Kappa = 0.05, for TST and chest X-ray an agreement of 95% with Kappa = 0.145, for QFT-IT and chest X-ray an agreement of 75 % and Kappa = -0.04. There wasn't any of the patients with a suspiscious Chest X-ray that had a positive TST and only one had a positive QFT-IT. Conclusion: We found a strong correlation between corticosteroid treatment and lower or indeterminate mitogen responses (QFT-IT). Therefore, we advise caution in the interpretation of a negative or an indeterminate QFT-IT test result in patients treated with corticosteroids since the test result might be falsely negative. The added value of Chest X-ray for the diagnosis of LTBI was questionable. A cost/benefit study seems necessary to determinate if the chest X-ray should be excluded from the LTBI screening-program