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P136. The clinical importance of in vitro interferon-gamma assay for differential diagnosis between intestinal tuberculosis and Crohn's disease

S.-K. Kim1, Y.-H. Kwon1, 1Kyungpook National University, Gastroenterology, Daegu, South Korea

Background

To diagnose between intestinal tuberculosis (ITB) and Crohn's disease (CD) is a difficult problem, because disease presentation and endoscopic findings mimic inflammatory conditions such as CD and malignancies. So we evaluated the usefulness of the QuantiFERON-TB Gold In-Tube test (QFN-GIT) for differential diagnosis between ITB and other inflammatory bowel diseases.

Methods

75 patients with abnormal endoscopic findings and gastrointestinal trouble were enrolled between October 2007 and December 2011. The QFN-GIT, comprises three tubes: a test tube containing antigens from ESAT-6, CFP-10 and part of the sequence of TB7.7; a positive control tube (containing phytohaemagglutinin); and a negative control tube. The three tubes are inoculated with the patient's blood, incubating for 16–24 hours, and the IFN-gamma concentration measured by an ELISA. We evaluated the usefulness of QFN-GIT blood test comparing the results to the final diagnosis.

Results

23, 9 and 42 patients were revealed to be positive, intermediate, and negative in the QFN-GIT. Among the 23 patients with positive results, 13 patients (56.5%) were finally diagnosed as ITB, 5 patients were diagnosed as infective enteritis, 2 patients were diagnosed as Behcet's disease (BD), 1 patients were diagnosed as TB lymphadenitis, and 2 patients were unspecific colitis. Of the 9 patients indeteminated group, 3 patients (33.3%) were diagnosed as CD, 2 patients (22.2%) were diagnosed as ITB, and 4 patients were diagnosed as unspecific colitis. 42 patients with negative group, 11 patients (26.2%) were diagnosed as CD, 9 patients (21.4%) were diagnosed as ITB, 3 patients diagnosed as ulcerative colitis, 2 patients diagnosed as BD and others were diagnosed as infective or unspecific colitis. The sensitivity and specificity of QFN-GIT for ITB were 54.2% and 64.2%, respectively. Positive and negative predictive values of QFN-GIT for ITB were 56.5% and 79.1%, respectively.

Conclusion

For differential diagnosis between CD and ITB, the diagnostic value of In Vitro Interferon-gamma Assay doesn't have effective evidence in this study.