Making a Positive Diagnosis of Intestinal Tuberculosis with the Aid of New Biologic and Histologic Features: How Far Have We Reached?

ABSTRACT

BACKGROUND: The diagnosis of intestinal tuberculosis (TB) and its differentiation from Crohn's disease (CD) remain a challenge. We review here in detail the various methods for the diagnosis of intestinal TB. SUMMARY: Colonoscopy findings in intestinal TB are useful and suggestive; histopathology of colonoscopic biopsies is contributory but rarely confirmatory. Increasing the number of colonoscopic biopsies increases the histological yield. Recent culture methods that have improved the yield for TB offer hope. Mycobacteria Growth Indicator Tube (MGIT) culture is now the standard of care as its yield is superior to that of the traditional Lowenstein-Jensen medium. Increasing the number of colonoscopic biopsy samples for MGIT culture can increase the yield. The culture and histology are complimentary. Even then a significant proportion of patients do not have a positive diagnosis of intestinal TB. Scoring systems have been developed with a sensitivity and specificity of 90 and 60%, respectively, but their utility in routine practice is yet to be established. Similarly, the ratio of visceral fat to total fat is helpful in differentiating CD from intestinal TB. Polymerase chain reaction has been used but its value seems uncertain. Gene Xpert® in an emerging technique that has been found to be useful in the diagnosis of pulmonary TB, and its utility in intestinal TB needs to be looked at. Newer technologies like TB-LAMP (loop-mediated isothermal amplification) need to be assessed in clinical studies. KEY MESSAGE Optimization of the present diagnostic tools (taking an adequate number of biopsies for histology and culture) and study of newer techniques to learn their actual utility seems to be the way forward.