The Usefulness of In Vitro Interferon-γ Assay for Differential Diagnosis between Intestinal Tuberculosis and Crohn's Disease

Abstract

It is difficult to clinically and endoscopically differentiate intestinal tuberculosis (ITB) and Crohns disease (CD). The aim of this study was to evaluate the usefulness of in vitro interferon-gamma (INF-gamma) assay for differential diagnosis between ITB and CD. Sixty patients for whom differential diagnosis between ITB and CD was difficult were enrolled between January 2007 and January 2009. The INF-gamma-producing T-cell response to early secreted antigenic target 6 and culture filtrate protein 10 were measured by T-SPOT.TB blood test in vitro. We evaluated the usefulness of T-SPOT.TB blood test by comparing its results with the final diagnosis. Twenty and forty patients were revealed to be positive and negative in T-SPOT.TB blood test, respectively. Of the 20 patients found to be positive, 12 patients (60%) were finally diagnosed as ITB, 6 patients as CD, and 2 patients as Behcets enterocolitis. Of the 40 patients with negative results, 38 patients (95%) were diagnosed as CD; one as Behcets enterocolitis; one as nonspecific colitis; none as ITB. The sensitivity and specificity of T-SPOT.TB blood test for ITB were 100% and 83.3%, respectively. Positive and negative predictive values of T-SPOT.TB blood test for ITB were 60.0% and 100%, respectively. When differential diagnosis between ITB and CD is difficult, T-SPOT.TB blood test may be a helpful and rapid diagnostic tool to exclude ITB. Prospective large-scaled studies are required for further evaluation of the usefulness of T-SPOT.TB blood test for differential diagnosis between ITB and CD.