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BackgroundTumor necrosis factor alpha (TNFα) is a key cytokine in both the pathogenesis of inflammatory bowel disease (IBD) and rheumatoid arthritis (RA) and the host defense against tuberculosis (TB). Consequently, anti-TNFα medications result in an increased risk of latent TB infection (LTBI) reactivation. Here, we sought to evaluate the factors affecting the results of QuantiFERON-TB Gold In-Tube (QFT-GIT) assay as a screening tool for LTBI.MethodsWe conducted an observational, retrospective study in patients with IBD and RA who underwent LTBI screening using QFT-GIT at UMass Memorial Medical Center between 2008 and 2016 prior to initiation of anti-TNF medications.ResultsWe included 107 and 89 patients with IBD and RA, respectively. We found that a higher proportion of IBD patients had indeterminate QFT-GIT result compared to RA patients. Furthermore, we found that the majority of patients with indeterminate results were tested during an acute flare of IBD (88%) and while taking corticosteroids. Of all patients receiving ≥20 mg equivalent prednisone dose (n=32), 63% resulted in indeterminate QFT-GIT, compared to only 6% indeterminate testing in patients receiving <20 mg of equivalent prednisone dose (n=164, P<0.001). There was no correlation between indeterminate results and age, gender, disease duration, or distribution, or smoking status within each population.ConclusionWe observed that high-dose corticosteroids may affect QFT-GIT outcomes leading to a high proportion of indeterminate results. We propose that IBD patients should be tested prior to initiation of corticosteroids to avoid equivocal results and prevent potential delays in initiation of anti-TNF medications.