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P127. Diagnosis of latent tuberculosis in patients with inflammatory bowel disease: Prospective comparison between tuberculin skin test and IGRA test QuantiFERON TB-Gold®

P127. Diagnosis of latent tuberculosis in patients with inflammatory bowel disease: Prospective comparison between tuberculin skin test and IGRA test QuantiFERON TB-Gold®

J. Machado, P. Ministro, R. Araújo, E. Cancela, A. Castanheira, A. Silva

H. S. Teotónio, Viseu, Portugal

Introduction: Anti-tumor necrosis factor-α (TNF-α) therapies are being increasingly used for treatment of Inflammatory Bowel Diseases. TNF-α is essential for host defence against Mycobacterium Tuberculosis (Mt), thus, screening for latent tuberculosis is mandatory before starting those therapies. Recently, Interferon Gamma Release Assays (IGRA) tests have been developed for this propose as an alternative to the traditional Tuberculin Skin test (TST) but their role needs to be validated specially in immunosuppressed patients.

Aims: Determine the agreement between TST and IGRA test Quantiferon TB-Gold in Tube® in an Inflammatory Bowel Diseases population according to their immunologic background.

Materials and Methods: A prospective study involving 24 patients with previous diagnosis of Inflammatory Bowel Disease, fulfilling criteria to initiate anti-TNFα treatment was conducted in our hospital. All patients were vaccinated with BCG, had a normal chest X-ray and excluded history of known tuberculosis contacts. Quantiferon TB-Gold inTube® was performed in a peripheral blood sample and registered as positive or negative. TST (Tuberculina PPD RT 23 SSI®) was measured 72 hours after subcutaneous inoculation of 2U.T. in patient's forearm and repeated 1 week later if negative. A 5 mm cut-off was defined.

Results: Nine positive results were registered using TST (37.5%) and only four using Quantiferon TB Gold inTube® (16.7%). Agreement between tests in all study group was 70.83%, kappa = 0.300. In the immunosuppressed group was registered one positive test using TST and other two using Quantiferon TB-Gold inTube® (agreement 78.57%, Kappa = −0.105). Among immunocompetent patients, seven positive TST tests were registered and three positive tests with Quantiferon TBGold inTube® (agreement 60%, kappa = 0.310). During follow-up (18 months), 18 patients initiated therapy with anti-TNFα agents, 9 completed two months of anti-tuberculosis treatment (Isoniazide) before starting anti-TNFα, only one developed adverse effects (hepatotoxicity) and no active tuberculosis was detected during this period.

Conclusion: The agreement between these two tests was low in our study group. Immunosuppressed patients subgroup had the lowest agreement. Unlike we expected, we obtained more positive results with TST than with Quantiferon TB-Gold inTube® in immunosuppressed subgroup.