The role of in vitro interferonγ-release assay in differentiating intestinal tuberculosis from Crohn's disease in China

Abstract

Aim: Intestinal tuberculosis (ITB) and Crohn's disease (CD) have overlapping clinical, radiographic, endoscopic and histologic features, which makes the distinction between these two disease entities a great challenge in tuberculosis-endemic countries. The aim of the study was to investigate the value of in vitro interferonγ release assay (T-SPOT.TB) in differentiating ITB from CD. Methods: From June 2008 to February 2010, a total of 93 consecutive patients with undetermined ITB or CD were prospectively recruited. Clinical, endoscopic, histologic and therapeutic responses were longitudinally monitored at follow-up evaluation until the final definite diagnosis has been reached. Results: After a median of 6 months' follow-up (interquartile range [IQR], 3.0 to 7.5 months), definitive diagnosis was achieved in 84 of the 93 patients (90%), with 19 having ITB and 65 having CD. On univariate analysis, a long duration of illness, chronic diarrhea, and anemia were significantly more common in CD (P < 0.05). While night sweat, ascites, pulmonary lesions, circumferential ulcer on endoscopy, ileo-cecal valve involvement and epithelioid granulomas were significantly more common in ITB (P < 0.05). On multivariate analysis, T-SPOT.TB (Hazard ratio 7.0, 95% confidence interval [CI] 1.9–25.7) was found to be a good predictor for ITB diagnosis. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) of T-SPOT.TB were 84.2%, 75.4%, 50.0%, and 94.2%, respectively. Conclusions: When differentiating ITB and CD in tuberculosis-endemic regions, T-SPOT.TB blood test may be a helpful and practical diagnostic tool for its high NPV to rule out ITB.