Do Additional Colonoscopic Biopsies Increase the Yield of Mycobacterium Tuberculosis Culture in Suspected Ileo-colonic Tuberculosis?

Background: Isolation of Mycobacterium tuberculosis on culture is vital for differentiating intestinal tuberculosis (ITB) from Crohn's disease (when histology is not diagnostic) and for diagnosis of multidrug-resistant tuberculosis. The current yield of TB culture (< 50%) from colonoscopic biopsy tissue is not satisfactory.

Aim: To determine whether more colonoscopic biopsies can increase the yield of TB culture in patients with ITB.

Methods: In this prospective study, in patients who underwent colonoscopy for suspected ITB, four biopsies were taken (container 1) followed by an additional four biopsies (container 2) for TB culture, from involved regions. The culture was done using Mycobacterium Growth Indicator Tube (MGIT) 960. A final diagnosis of ITB was made if TB culture was positive, there was unequivocal histological evidence of TB, or there was unequivocal evidence of TB elsewhere in the body, in the absence of another diagnosis.

Results: Of 182 patients enrolled (mean age 37.5 [SD 17.2] years; 93 [51.5%] women), 70 (38.4%) were finally diagnosed to have ITB. MGIT culture was positive in 29 (41.4%), 27 (38.5%), and 37 (52.8%) of 70 patients from containers 1, container 2, and combined eight biopsies, respectively. The incremental yield of eight biopsies was 11.4% (95% confidence interval [CI] 5.1 to 21.3%) as compared to container 1 and 14.3% (95% CI 7.1 to 24.7%) as compared to container 2.

Conclusion: Additional four (total eight) colonoscopic biopsies improved the yield of TB culture positivity over four biopsies by 11.4% to 14.3%, to 52.8%; this increase is clinically useful.