Line Probe Assay Is Better Than CBNAAT for Diagnosis of Ileocolonic Tuberculosis: A Prospective Study

Abstract

Diagnosis of Ileocolonic Tuberculosis remains a challenge due to its nonspecific clinical and laboratory characteristics. Role of Line probe assay in Ileocolonic ulcers for the diagnosis of intestinal tuberculosis and Non Tubercular Mycobacterium is not well defined. We report the utility of Line Probe Assay (LPA) testing in patients with Ileocolonic ulcers and its comparison with Cartridge based nucleic acid amplification test (CBNAAT) and histopathology. Methodology: A prospective study of 35 patients with Ileocolonic ulcers detected during colonoscopy. Ileocolonic ulcer tissue was subjected to Line probe assay (GenoType Mycobacterium CM kit) for detection of Mycobacterium tuberculosis (MT) and Non tubercular Mycobacterium (NTM), CBNAAT (Gene Xpert), and Histopathology. Patients were followed up for six months and repeat colonoscopy was done for response of therapy and to assess diagnostic accuracy. Results: Out of 35 patients, 31 patients were analysed. 16 patients diagnosed to have TB were started on anti-tubercular treatment based on clinical presentation, LPA, CBNAAT and histopathology. 15 patients had other diagnosis. Sensitivity and specificity of LPA for diagnosis of ITB was 28.57% and   50%whereas The sensitivity of CBNAAT was 7.14% and the specificity was 100%.Histopathology was positive in 12 patients (38.7%). Positive predictive value of both LPA and CBNAAT were comparable. Conclusion: LPA provides an additional investigation in the armamentarium for the diagnosis of Ileocolonic tuberculosis .Although CBNAAT is generally recommended in the diagnosis of tuberculosis in extra-pulmonary specimens, utility of the same in the setting of Ileocolonic ulcers appears limited as demonstrated in this study.