Interferon-γ release assay in the diagnosis of latent tuberculosis infection in arthritis patients treated with tumor necrosis factor antagonists in Korea

The aim of this study was to evaluate the usefulness of the interferon-γ release assay (IGRA) for the diagnosis of latent tuberculosis infection (LTBI) in arthritis patients who received tumor necrosis factor (TNF) antagonist in Korea. The study involved 107 consecutive patients: 61 (57%) with ankylosing spondylitis and 46 (43%) with rheumatoid arthritis. Screening tests were performed including the tuberculin skin test (TST), the QuantiFERON-TB Gold In-Tube (QFT-IT) test, and chest radiography. A positive QFT-IT test result, regardless of TST results, was considered an indication for LTBI treatment. If the QFT-IT results were indeterminate, a positive TST was regarded as an indication for LTBI treatment. A Bacillus Calmette-Guérin (BCG) scar was found in 63 patients (59%). LTBI treatment was performed in 37 patients (35%), including 36 with positive QFT-IT results and one with indeterminate QFT-IT and positive TST results. No patients developed tuberculosis during a median of 18 months (range, 13–26 months) of TNF antagonist therapy. In 16 patients who had positive TST and negative QFT-IT results, TNF antagonists were given without LTBI treatment. Tuberculosis did not occur, even in these patients, during a median of 24.5 months (range, 15–33.5 months) of TNF antagonist therapy. IGRA may be used instead of TST for the diagnosis of LTBI in patients before starting TNF antagonists in countries where tuberculosis prevalence is intermediate and the BCG vaccination is mandatory at birth, such as in Korea.