Gene Xpert for Direct Detection of Mycobacterium Tuberculosis in Stool Specimens from Children with Presumptive Pulmonary Tuberculosis

Abstract

Background: Gene Xpert(GX) is a novel real time polymerase chain reaction (RT-PCR) assay which was endorsed by the World Health Organization (WHO) in 2011 for tuberculosis (TB) diagnosis and susceptibility to refampicin(RIF).

Objective: To evaluate GX for direct diagnosis of TB in stool samples from children with suspected pulmonary Tuberculosis (PTB).

Methods: Children older than one year and younger than 16 years with presumptive PTB were enrolled and classified to five clinical categories based on clinical, radiological, and laboratory findings: confirmed TB, probable TB, possible TB, Unlikely TB, and not TB. Two stool samples were collected from each child and tested for the presence of Mycobacterium tuberculosis (MTB) by GX and the obtained results were compared to Lowenstien-Jensen (LJ) culture as a gold standard.

Results: In total, 115 children were enrolled. 36 had been confirmed with TB, 61 probably TB, 10 possible TB, 5 unlikely TB, and 3 not TB. GX had a sensitivity of 83.33 and 80.56 % and specificity of 98.73 and 99.36 % by patients and samples respectively. GX was positive in 83.3% of confirmed TB as well as 1.6 and 0.8% of probable TB cases by patients and samples respectively.

Conclusions: GX provided timely results with quit acceptable sensitivity and good specificity compared to LJ culture. In this study, sensitivity calculations take into account only children with confirmed TB. GX could not detect TB in children with probable TB, so it should not be used alone for TB diagnosis. Further studies for GX stool protocol optimization and assessment is required.

Keywords: Children; Gene Xpert; Mycobacterium tuberculosis; Pulmonary tuberculosis.