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P148. Role of interferon gamma release assay (IGRA) in differentiating gastrointestinal tuberculosis from Crohn's disease

P. Kakkadasam Ramaswami, H. Joshi, N. Toke, C. Panackel, S. Mathai, Medical Trust Hospital, Department of Gastroenterology, Ernakulam, India

Background

The clinical, endoscopic, and histological features of Crohn's disease (CD) and Intestinal Tuberculosis (ITB) mimic each other so much that it becomes difficult to differentiate between them. The aim of our study was to assess the sensitivity and specificity of IGRA in differentiating the two diseases.

Methods

We prospectively included 53 patients with Ileo-colonic ulcers and 30 normal subjects as controls. Demographic, clinical, laboratory, endoscopic and histological features were noted. All patients were evaluated with a IGRA [QuantiFERON-GOLD TB (QGTB)]. Patients were diagnosed as either ITB or CD based on clinical, endoscopic and histologic criteria. Patients were followed up and a repeat colonoscopy was performed at the end of 3 months of treatment; diagnosis was revised if the patient did not demonstrate mucosal healing or an improvement when compared to the previous colonoscopy.

Results

Twenty-eight (52.8%) patietnts were male, and the mean age was 36.7 years (Range 10–81 years). A final diagnosis of CD was made in 35 patients (66%), ITB in 18 patients (34%). QGTB test was positive in 22 patients, of which 17 patients had a final diagnosis of ITB and 5 patients had CD. One patient who had a final diagnosis of Tuberculosis had a negative QGTB test. Of the 18 patients with Intestinal Tuberculosis, two patients also had evidence of disseminated Tuberculosis.

Table 1 shows the clinical characteristics of the patients. All 30 control subjects had a negative test. The sensitivity of the QGTB test was 94.4% and specificity was 85.7%. Positive Predictive Value was 77.2%, negative predictive value was 96.7%.

Table 1. Clinical characteristics of the two groups
CD (n = 35)TB (n = 18)
Male/Female18/1710/8
Mean age in years (range)32.7 (10–65)44 (18–81)
Abdomial pain30 (85%)17 (94%)
Bleeding PR8 (22.8%)00
Diarrhoea24 (68.5%)9 (50%)
Weight loss21 (60%)13 (72%)
Fever3 (8.5%)8 (44%)
Stricturing disease8 (23%)00
Fistulizing disease6 (17%)1 (5.5%)

Conclusion

The QGTB Test is both sensitive and specific for diagnosing Gastrointestinal Tuberculosis and can be useful in differentiating Tuberculosis from Crohn's Disease.