QuantiFERON TB Gold Testing for Tuberculosis Screening in an Inflammatory Bowel Disease Cohort in the United States

Background: Reactivation of latent Mycobacterium tuberculosis (TB) is a rare, yet devastating infectious complication associated with anti-tumor necrosis factor alpha (TNF-alpha) therapy. We evaluated the performance of the QuantiFERON TB Gold test (QFT-G) for TB screening in a cohort of inflammatory bowel disease (IBD) patients in the United States. Methods: We performed a retrospective, observational study of patients initiated and/or maintained on an anti-TNF-alpha agent in a single IBD referral center and recorded the frequency and the test results of QFT-G testing and the rate of TB reactivation. Results: 512 QFT-G tests were done in 340 patients. Five patients (1.5%) had a positive, nine (2.7%) indeterminate, and 326 patients (95.8%) had a negative QFT-G. After a mean follow-up of 17 months there was one case of TB reactivation (0.3%). The use of immunosuppressive therapy or anti-TNF therapy at the time of testing did not affect the results of the QFT-G testing. Test-retest had substantial concordance (kappa = 0.72). 25% of patients (n = 85) had TST testing. Concordance between the TST and QFT-G was found to be moderate (kappa = 0.4152, P = 0.0041). Conclusions: Most patients with negative QFT-G tolerated anti-TNF therapy with no evidence of TB reactivation. Concomitant use of immunosuppressive therapy or anti-TNF did not seem to affect QFT-G results. One patient had an indeterminate QFT-G while on infliximab and later developed miliary TB. Concordance with TST is moderate.