Diagnosis of Crohn's disease in India where tuberculosis is widely prevalent

To define the parameters that positively predict diagnosis of Crohn's disease (CD) and differentiate it from gastrointestinal tuberculosis (GITB).

This prospective study over 3 years was carried out in the consecutive Indian patients with definite diagnosis of CD and equal numbers of patients with definite diagnosis of GITB. Demographic, clinical, laboratory, morphological and histological features were noted in all the patients. Serological tests such as p-ANCA, c-ANCA, IgA ASCA and IgG ASCA, were performed. Endoscopic biopsy and/or surgical tissue specimens were subjected to smear and culture for acid-fast bacilli (AFB) and tissue polymerase chain reaction for tuberculosis (TB PCR). Diagnosis of CD and GITB was based on the standard criteria. Data were analyzed using univariate Chi-square test and multiple logistic regression (MLR).

The study is comprised of 26 patients with CD (age 36.6 +/- 8.6 year, male:female, 16:10) and 26 patients with GITB (age 37.2 +/- 9.6 year, male:female, 15:11). The following clinical variables between the two groups (CD vs TB) were significant in univariate analysis: duration of symptoms (58.1 +/- 9.8 vs 7.2 +/- 3.4 mo), diarrhoea (69.2% vs 34.6%), bleeding per rectum (30.7% vs 3.8%), fever (23.1% vs 69.2%), ascites (7.7% vs 34.6%) and extra-intestinal manifestations of inflammatory bowel disease (61.5% vs 23.1%). Of these, all except ascites and extra-colonic manifestations were found statistically significant by MLR. Accuracy of predicting CD was 84.62% based on the fever, bleeding P/R, diarrhoea and duration of symptoms while it was 63.4% when histology was reported as inflammatory bowel disease and 42.3% when there was recurrence of disease after surgery. Accuracy of predicting GITB was 73.1% when there was co-existing pulmonary lesions and/or abdominal lymphadenopathy; 75% when tuberculosis was reported in histology; 63.4% when granuloma was found in histology; 82.6% when TB PCR was positive; and 61.5% when smear and/ or culture was positive for AFB. Serological test was not useful in differentiation of CD from GITB. Positivity rates for CD and GITB were: p-ANCA- 3.8% and 3.8%, c-ANCA- 3.8% and 0%, IgA ASCA- 38.4% and 23.1%, and IgG ASCA- 38.4% and 42.3%, respectively.

Simple clinical parameters like fever, bleeding P/R, diarrhoea and duration of symptoms have the highest accuracy in differentiating CD from GITB.