Levels of TB-IGRA may help to differentiate between intestinal tuberculosis and Crohn’s disease in patients with positive results

Abstract

Aim: The aim of this study was to investigate the significance of positive tuberculosis interferon gamma release assay (TB-IGRA) in the differential diagnosis of intestinal tuberculosis (ITB) and Crohn’s disease (CD) patients, and to find a suitable threshold to help distinguishing CD from tuberculosis (TB), so as to provide better recommendations for clinical treatment. Methods: A retrospective study was performed including 484 patients who underwent TB-IGRA testing for suspected CD or ITB treated in the Shanghai Tenth People’s Hospital of Tongji University between January 2015 and May 2018. According to the diagnostic criteria, 307 patients, including 272 CD and 35 ITB patients, were recruited for the final analysis. We comprehensively and systematically collected their clinical manifestations, and analyzed the influence of TB-IGRA values referring to diagnosis criteria, and the possible causes of false positives. The receiver operator characteristic (ROC) curve and the cut-off value were applied to distinguish between ITB and CD patients. Results: Of the 56 patients with suspected CD enrolled, 23 were finally diagnosed with CD and 33 with ITB. In patients with TB-IGRA ⩾ 100 pg/ml, 4 cases were CD and 29 cases were ITB, while 19 cases were CD and 4 cases were ITB in patients with TB-IGRA < 100 pg/ml ( p < 0.05). TB-IGRA ⩾ 100 pg/ml indicated a high possibility of TB infection, with a sensitivity of 88% and a specificity of 74%. Three out of the four CD patients with TB-IGRA ⩾ 100 pg/ml had a history of tuberculosis, while only 1 of the 19 CD patients with TB-IGRA < 100 pg/ml had a history of tuberculosis ( p < 0.05). The average duration of ITB was 7 months, and that of CD was 46.8 months, thus a significant difference ( p < 0.05) was observed. Perianal lesions such as anal fistula or abscess were found in all CD patients. Among ITB patients, 8 out of 15 patients with TB-IGRA ⩾ 400 pg/ml experienced weight loss, while only 1 out of 18 patients with TB-IGRA < 400 pg/ml underwent weight loss ( p < 0.05). Conclusion: Patients with CD have longer duration of disease, and perianal lesions are more common in CD. ITB patients with TB-IGRA ⩾ 400 pg/ml experience weight loss more readily, which indicates that TB-IGRA value may be correlated positively with the severity of ITB. In patients with CD and ITB, TB-IGRA = 100 pg/ml may be a cut-off value of TB-IGRA. For patients with TB-IGRA ⩾ 100 pg/ml, it is recommended to use diagnostic anti-TB treatment first. Comprehensive analysis and judgment are required for patients with TB-IGRA from 14 pg/ml to 99 pg/ml. TB-IGRA false positivity may occur in patients with a history of TB infection.