Prospective evaluation of the clinical utility of interferon-γ assay in the differential diagnosis of intestinal tuberculosis and Crohnʼs disease

Abstract

Distinguishing intestinal tuberculosis (ITB) from Crohn's disease (CD) is challenging. This study prospectively evaluated the clinical utility of the QuantiFERON-TB gold test (QFT) in the differential diagnosis of ITB and CD, and compared it with the clinical utility of the tuberculin skin test (TST). Patients with suspected ITB or CD on colonoscopic findings were enrolled from 13 hospitals in Korea between June 2007 and November 2008. A QFT and TST were performed. When the initial diagnosis was not confirmed, 2-3 months of empiric antituberculous therapy was administered. In all, 128 patients were analyzed; 64 patients had ITB and 64 patients had CD. The median age of patients with ITB was greater than the patients with CD (47 years versus 31 years, P < 0.001). The positive rate for the QFT and TST (≥10 mm) in patients with ITB was significantly higher than patients with CD (67% versus 9% and 69% versus 16%, respectively; P < 0.001). The QFT and TST had good agreement (κ = 0.724, P < 0.001). The diagnostic validity of QFT in ITB had a 67% sensitivity, 90% specificity, 87% positive predictive value, and 73% negative predictive value. There was no difference in these parameters between the QFT and TST. The likelihood ratio for a positive QFT was higher than a positive TST in the diagnosis of ITB (7.1 and 4.4, respectively). The QFT is a limited but useful diagnostic aid in combination with the TST in the diagnosis of ITB.