The purpose of this study is to evaluate the value of Quantiferon-TB Gold (QFT-G) assay in the screening for latent tuberculosis infection (LTBI) in rheumatologic patients due to start or on treatment with TNFα antagonists. The results of QFT-G will be compared to tuberculin skin testing (TST) and correlated to clinical and demographic data. The study hypothesis is that the inclusion of QTF-G in the screening strategy will allow a more accurate assessment of LTBI infection.