Role of interferon-gamma release assays (IGRAs) for the screening of latent tuberculosis infection in patients candidates for TNF-α antagonist

Background: Tumor necrosis factor-α (TNF-a) inhibitors are associated with an increased risk of reactivation of latent tuberculosis infection (LTBI); thus, the guidelines recommends TB screening for all patients before starting anti-TNF-α therapy.The use of tuberculin skin test (TST) is controversial because of the immunosuppressive treatment may lead to false-negative TST results and previous BCG-vaccination produces false-positive. The introduction in clinical practice of the interferon-gamma release assays (IGRAs) has opened new perspectives for diagnosis of LTBI.The aim of the study was to investigate the performance of QuantiFERON-TB Gold In Tube assay (QFT-GIT) for the diagnosis of LTBI in patients with an immune-mediated inflammatory diseases candidates for anti-TNF-α therapy. Methods:We enrolled 195 patients with rheumatoid arthritis (n=72), psoriatic arthritis (n=40), psoriasis (n=41), ankylosing spondylitis (n=10), Crohn’s disease (n=18), and Behcet’s disease (n=8). Screening included: clinical evaluation, chest X-ray,TST and QFT-GIT. Results: Of the 195 patients, 32 (16.4%), 137 (70.2%) and 26 (13.3%) tested positive, negative and indeterminate with QFT-GIT test, respectively. The level of agreement between two tests was 81.6 % (k=0.55). Among the screened patients, 38 (19%) were considered to have LTBI and received isoniazid treatment, while 31 patients (16%) showed discordant results between two tests. Univariate analysis showed an association between BCG vaccination and discordant TST-positive/QFT-GIT-negative results (OR=6; 95%CI: 2.3-37.1; p<0.001); no association was observed between the immunosuppressive therapy and discordant TST-negative/QFT-GIT-positive results (OR=0.16; 95%CI: 0.01-1.8; p<0.09). Conclusions: Our results suggest that QFT-GIT may be helpful for the diagnosis of LTBI in patients candidates for anti-TNF-α treatment because of its performance seems to not be affected by any type of immunosuppression.