The aims of the current study were (a) to determine whether TNF-α antagonists affect the QTF test; (b) to determine how the QTF test performs in comparison to the TST in rheumatoid arthritis (RA) patients treated with TNF-α antagonists, RA patients who are not treated with TNF-α antagonists, rheumatology patients who had had proven tuberculosis, and healthy controls; and (c) to assess the QTF test in leprosy patients, another group of patients infected with mycobacteria. The gene discussed is TNF; the disease is leprosy.