Quantiferon TB Gold and tuberculin skin tests for the detection of latent tuberculosis infection in patients treated with tumour necrosis factor alpha blocking agents

Objectives The risk of activation of latent tuberculosis infection (LTBI) is increased in patients treated with anti-TNF-alpha drugs. Tuberculin skin test (TST) and Quantiferon-TB Gold test (QFT) are used to detect LTBI before and during anti-TNF-alpha treatment. We describe here a relation of these tests at various timepoints and also longitudinal QFT data. Methods Study group consisted of 305 patients with several rheumatic inflammatory diseases treated and/or scheduled for anti-TNF-alpha drugs. The QFT was performed in 303 patients during therapy and in 177 patients also during screening. The TST was used in 284 patients. Both tests sinuiltaneously were utilised in 360 instances. Results Twenty-two patients were QFT positive; 3.9% before and 5.9% during anti-TNF-alpha treatment. Two patients who became QFT positive developed active tuberculosis. The TST was positive in 42% and 38% of patients before and during treatment, respectively. There was poor agreement between the two tests. Patients on glucocorticoids had a negative TST more frequently. The IFN-gamma response to mycobacterial antigens significantly increased after application of tuberculin, but never reached the positive threshold. There was a significant increase in mitogen-induced IFN-y production after initiation of anti-TNF-alpha therapy. Conclusion Poor correlation between the QFT and TST renders the TST non-specific for LTBI. QFT is more specific to detect LTBI and conversion to a positive result may predict active TB. An increase in IFN-gamma production in response to nzycobacterial antigens is seen when the TST is performed before the QFT. Mitogen-induced IFN-gamma production increases after initiation of anti-TNF-alpha therapy.