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P197. Is the tuberculin skin test alone accurate in moderate-to-severe BCG vaccinated patients with inflammatory bowel disease to test for latent tuberculosis?

P.A. Golovics1, A. Szabo1, M. Mandel1, A. Gyurcsanyi1, K. Kristof2, Z. Vegh1, A. Mohas1, B. Szilagyi1, Z. Kurti1, B. Csako1, L. Kiss1, B. Lovasz1, K. Gecse1, P. Lakatos1, 1Semmelweis University, 1st Department of Medicine, Budapest, Hungary, 2Semmelweis University, Institute of Medical Microbiology, Budapest, Hungary

Background

There are few data available on effect of immunomodulator/biological therapy on the accuracy of tuberculin skin test (TST, Mantoux skin test) and interferon-gamma release assay (IGRA) in BCG vaccinated immunosuppressed IBD patients. Our aim was to define the accuracy of the TST and IGRA tests in a BCG vaccinated referral IBD cohort treated with immunosuppressives and/or biologicals.

Methods

Data of 90 consecutive moderate-to-severe IBD (77 CD, 13 UC) patients were analyzed (male/female: 42/48, median age at diagnosis: 23.0; SD: 10.02 years, duration: 7.0; SD:6.1 years). Patients were treated with immunosuppressives (azathioprine, steroids) and/or anti-TNF therapy. Blood samples for IGRA were collected during routine laboratory testing pearalel with TST. The result of TST was determined according to international guidelines. Both in- and outpatient records were collected and comprehensively reviewed.

Results

TST positivity rate was 25.8%, 23.6%, 14.6% or 13.5% with cut-off values of 5, 10, 15 and 20 mm. IGRA positivity rate was 8.1% with indeterminate result in 1.2%. The correlation between TST and IGRA was significant, with moderate-to-good kappa values if TST results were >15 mm (kappa: 0.41–0.45, p < 0.001). If TST 15 or 20 mm is defined as TST positivity an additional 10.3% and 9% of IBD patients required a pulmonologists consultation. There was no association between the type and number of immunomodulators used or any disease phenotype characteristics and the TST or IGRA results. Importantly, smoking was identified as a risk factors for TST but not IGRA positivity (OR: 4.35, 4.15 and 4.92, p = 0.012, p = 0.029 and 0.018 for TSTcut-off 10, 15 and 20 mm).

Conclusion

The TST and IGRA are partly complimentary methods and accuracy is acceptable also in BCG vaccinated and immunosuppressed IBD patients. A TST of >15 mm should be used as a cut-off to identify patients at risk for latent TB in these patients. Smoking is a risk factors for TST positivity.