Diagnostic Accuracy of Xpert Mtb/Rif Assay in Stool Samples in Intrathoracic Childhood Tuberculosis

Background: The study aims at finding out usefulness of Xpert in stool samples in children, as they usually swallow their sputum. It also simultaneously compares the results of stool Xpert with Xpert, smear and culture in gastric lavage and sputum samples. Materials and methods: A diagnostic accuracy study included children (< 15 years) with probable tuberculosis. Induced sputum, gastric aspirate and stool samples each were subjected to Xpert, AFB stain and culture. Diagnostic utility of stool Xpert was calculated with reference to liquid culture in sputum or gastric aspirate as gold standard. Results: The study included 100 children. Stool Xpert was positive in 4 cases (4%). Overall cultures positivity was 26%. The total yield including culture and Xpert (sputum or gastric aspirate) was 45%. The sensitivity of stool Xpert was 11.54% and specificity 98.65% as compared to culture. There was association of stool Xpert positivity with sputum AFB (p 0.024), sputum Xpert (p 0.004) and gastric aspirate Xpert (p 0.039), while there was no significant association with X-ray pattern or malnutrition. Conclusion: Stool sample for Xpert cannot replace gastric aspirate and induced sputum for diagnosis, and hence should not be used as a first line test.