4482 Usefulness of polymerase chain reaction for the differential diagnosis of intestinal tuberculosis and crohn's disease.

Abstract

Background & Aim: The definite diagnosis of intestinal tuberculosis (I-TB) is made by histological evidence of caseating granulomas or acid-fast bacilli, or growth of M. tuberculosis on culture of biopsy specimens. It is often difficult, however, to differentiate I-TB from Crohn's disease (CD) when all of the three tests were negative. The aim of this study was to evaluate the usefulness of M. tuberculosis complex-polymerase chain reaction (TBCPCR) for the differential diagnosis of I-TB and CD. Methods: We obtained biopsy specimens from 32 patients with I-TB and 29 patients with CD. Ziehl-Neelsen stain, M. tuberculosis culture and TBC-PCR were carried out in all patients. TBC-PCR was also performed with normal colonic specimens obtained from 22 patients with colonic polyps as the control. TBCPCR was done with DNA extracted from the paraffin-embedded tissues in all cases. Four pairs of oligonucleotide primers (Bioneer, Korea) were used for the nested PCR at the two different sites of IS6110 insertion element of M. tuberculosis complex. Results: The TBC-PCR gave positive results in 23 (72%) of 32 patients with I-TB, 3 (10%) of 29 patients with CD, and 3 (14%) of 22 normal controls, yielding a sensitivity of the TBC-PCR on biopsy specimens of 72% and a specificity of 88%. In patients with I-TB, the sensitivity of culture, acid-fast bacilli stain and caseating granulomas were 44%, 25% and 9%, respectively. When all of these three tests were combined, the sensitivity rose to 63%. In addition, among the 12 I-TB patients with the negative result in all of the three conventional tests, 8 (67%) were PCR-positive. Therefore when the result of TBC-PCR was combined with that of histological examination and culture, the sensitivity became higher upto 88%. The positive rate of TBC-PCR was 100% in patients showing caseating granulomas or acid-fast bacilli on histological examination, and 64% in culture-positive patients. Conclusions: TBC-PCR is a very sensitive method for the diagnosis of I-TB. Therefore, combining of TBC-PCR with conventional methods might be helpful in differentiating I-TB from CD.