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P097. Interferon-gamma release assay or tuberculin skin test in inflammatory bowel disease patients – which is reliable

Y. Ozen Alahdab1, A. Kedrah1, S. Ilhan1, Y. Yilmaz1, O. Yonal1, H. Alahdab2, O. Atug1, N. Imeryuz1, H. Over Hamzaoglu1

1Marmara University Hospital, Istanbul, Turkey; 2Anadolu Medical Center, Kocaeli, Turkey

Introduction: Detection of latent tuberculosis (LTB) is important before starting immunosuppressant or biological agents in patients with inflammatory bowel disease (IBD). Screening is recommended, even in low-endemic areas. No gold standards exist for detecting LTB. Conflicting recommendations are provided by current literature for diagnostic screening tests such as tuberculin skin test (TST) and interferon-gamma release assay (IGRA).

Objective: To evaluate interferon-gamma release assay, as opposed to Tuberculin skin test, for detection of LTBI.

Methods: We evaluated a total of 105 IBD patients (52 Crohn disease, 51 ulcerative colitis and 2 indeterminate colitis). Twenty seven percent of IBD patients were under immunosuppressive therapy. Fifty four healthy controls were included. Both TST and IGRA (QuantiFERON®-TB Gold In-Tube; QFT) were performed on 159 subjects.

Results: There were no significant differences in age, sex, history of Bacille Camette-Guerin vaccination between the two groups. There were significantly more anergic tests in patients not receiving immunosuppressive therapy than in controls (30.7% vs 9.3% p = 0.013). No significant difference was detected regarding the frequencies of IGRA positivity between the two groups (37.3% vs 27.8%, p > 0.05). In patients group, among those having IGRA positive results 66.6% TST positivity was detected. On the other hand, in control group, this percentage was 92.8% (p = 0.036).

Conclusion: In Turkey, where tuberculosis is relatively frequent, detecting LTB infection is vital before starting immunosupressants. We concluded that TST among immunosupressed patients showed a high incidence of anergy compared to healthy controls. On the other hand, IGRA showed positivity which did not differ significantly between the two groups. Accordingly, using IGRA instead of TST in immunosupressed patients may lead to more accurate detection of LTB infections than TST.