Evaluation of the usefulness of interferon-gamma release assays and the tuberculin skin test for the detection of latent Mycobacterium tuberculosis infections in Korean rheumatic patients who are candidates for biologic agents

Aim: The aim of this study was to evaluate the occurrence of active tuberculosis (TB) in patients who received both an interferon-gamma release assay (the QuantiFERON-TB Gold In-Tube test [QFT-GIT]) and tuberculin skin test (TST) in comparison with those who received QFT-GIT or TST alone for the detection of latent TB infection (LTBI). Methods: In total, 842 patients who received QFT-GIT or TST and used biologic agents between January 2007 and December 2012 were recruited to determine the usefulness of LTBI screening tests. The incidence of active TB was calculated relative to the LTBI screening method as the number of events per 100 000 person-years exposure. Results: TB occurred in two of the patients who complied with an LTBI prophylaxis strategy. The TB incidence in the group that received both QFT-GIT and TST was 151.05 (95% confidence interval [CI] 150.11-151.98)/100 000 person-years, and the incidence was 169.78 (95% CI 168.73-170.84)/100 000 person-years in the group that received only TST. Conclusion: TB occurred even in some patients who received LTBI prophylaxis in compliance with national guidelines. The incidence of TB in patients who received either the QFT-GIT plus TST prophylaxis strategy or the TST prophylaxis strategy alone was higher than the annual incidence of the general population of the Republic of Korea. It is not possible to conclude which of the LTBI prophylaxis strategies is superior.