Quantiferon-TB Gold in tube assay for the screening of tuberculosis before and during treatment with tumor necrosis factor alpha antagonists

Introduction: The usefulness of interferon-gamma (IFN-gamma) release assays for tuberculosis screening before tumor necrosis factor-alpha (TNF-alpha) antagonists and for monitoring during treatment is a contraversial issue. The aims of this study were to determine whether TNF-alpha antagonists affect the results of the Quantiferon-TB Gold in-tube assay (QTF); to assess how QTF performs in comparison with the tuberculin skin test (TST) in rheumatoid arthritis (RA) patients who are about to start treatment with TNF-alpha antagonists, RA patients who are not candidates for treatment with TNF-alpha antagonists, rheumatology patients with confirmed current or past tuberculosis infection, and healthy controls, and to determine the specificity of the QTF test to differentiate leprosy patients, another group of patients infected with mycobacteria. Methods: The 38 RA patients who were prescribed TNF-alpha antagonists, 40 RA patients who were not considered for TNF-alpha antagonist use, 30 rheumatology patients with a history or new diagnosis of tuberculosis, 23 leprosy patients, and 41 healthy controls were studied. QTF and TST were done on the same day, and both were repeated after a mean of 3.6 +/- 0.2 months in patients who used TNF-alpha antagonists. Results: Treatment with TNF-alpha antagonists did not cause a significant change in the QTF or TST positivity rate (34% versus 42%; P = 0.64; and 24% versus 37%; P = 0.22). Patients with leprosy had a trend for a higher mean IFN-gamma level (7.3 +/- 8.0) and QTF positivity (61%) than did the other groups; however, the difference was not significant (P = 0.09 and P = 0.43). Conclusions: Treatment with TNF-alpha antagonists does not seem to affect the QTF test to an appreciable degree. The higher IFN-gamma levels in leprosy patients deserves further attention.