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Abstract

The activation of latent tuberculosis (TB) can be a problem in patients with inflammatory bowel disease (IBD) treated with biologicals. So far, the tuberculin skin test (TST) and chest x-rays were routinely used to detect TB, and used in various IBD trials. Our paper (Am J Gastroenterol 2008;103:2799–2806) described the poor correlation between an interferon (IFN)-γ release assay (IGRA; Quantiferon-TB Gold In-TubeTest [QFT-G-IT]) and the TST. There are practical disadvantages of the TST (2 visits), and the false-positive results in BCG-immunized people and the false-negative results TST in patients under immunosuppression clearly limit the usefulness of this test.In our study, blood samples were taken and then the TST was performed. Thus, the TST was not able to influence the QFT-G-IT (theoretical risk of a false-positive result). Meanwhile, we gained more experience with QFT-G-IT in daily practice. So far, we have not yet observed TB in patients with a negative test. However, others showed that QFT-G-IT may not detect latent or active TB, especially in case of lymphocytopenia (J Infect Chemother 2007;13:414–417; Infection 2008;Dec 10 [Epub ahead of print]). Unfortunately, there is no gold standard for the diagnosis of latent TB. The relatively low positive predictive value of the IGRAs in active TB, however, may limit their usefulness in clinical practice (Chest 2007;132:959–965). Because there may be a small risk that the QFT-G-IT overlooks latent and active TB, the test does not replace a carefully clinical workup of our patients. The indeterminate results of QFT-G-IT in some patients are further limitations of this test. IGRAs certainly improved our diagnostic yield, but are still not optimal. The activation of latent tuberculosis (TB) can be a problem in patients with inflammatory bowel disease (IBD) treated with biologicals. So far, the tuberculin skin test (TST) and chest x-rays were routinely used to detect TB, and used in various IBD trials. Our paper (Am J Gastroenterol 2008;103:2799–2806) described the poor correlation between an interferon (IFN)-γ release assay (IGRA; Quantiferon-TB Gold In-TubeTest [QFT-G-IT]) and the TST. There are practical disadvantages of the TST (2 visits), and the false-positive results in BCG-immunized people and the false-negative results TST in patients under immunosuppression clearly limit the usefulness of this test. In our study, blood samples were taken and then the TST was performed. Thus, the TST was not able to influence the QFT-G-IT (theoretical risk of a false-positive result). Meanwhile, we gained more experience with QFT-G-IT in daily practice. So far, we have not yet observed TB in patients with a negative test. However, others showed that QFT-G-IT may not detect latent or active TB, especially in case of lymphocytopenia (J Infect Chemother 2007;13:414–417; Infection 2008;Dec 10 [Epub ahead of print]). Unfortunately, there is no gold standard for the diagnosis of latent TB. The relatively low positive predictive value of the IGRAs in active TB, however, may limit their usefulness in clinical practice (Chest 2007;132:959–965). Because there may be a small risk that the QFT-G-IT overlooks latent and active TB, the test does not replace a carefully clinical workup of our patients. The indeterminate results of QFT-G-IT in some patients are further limitations of this test. IGRAs certainly improved our diagnostic yield, but are still not optimal. Comparison of Interferon-Gamma Release Assay Versus Tuberculin Skin Test for Tuberculosis Screening in Inflammatory Bowel DiseaseGastroenterologyVol. 136Issue 4PreviewSchoepfer AM, Flogerzi B, Fallegger S, et al. (Department of Gastroenterology, Inselspital/University of Bern, Bern, Switzerland). Comparison of interferon-gamma release assay versus tuberculin skin test for tuberculosis screening in inflammatory bowel disease. Am J Gastroenterol 2008;103:2799–2806. Full-Text PDF