Comparison of gastric lavage/sputum and stool specimens in the diagnosis of pediatric pulmonary tuberculosis- A pilot study

Abstract

Background and objective: Global TB report 2021 mentions 11 % prevalence of pediatric TB, whereas 5.65% of the cases were reported from India in 2020. India features in the list of TB high burden countries, HIV-TB high burden and MDR-TB high burden countries. The diagnosis of pulmonary tuberculosis in children is difficult as they tend to swallow the sputum, invasive techniques of gastric aspirates needs to be followed and the disease itself is paucibacillary. The disease progresses rapidly in young children and hence rapid diagnosis is needed. Obtaining appropriate respiratory samples for diagnosis is difficult especially in primary care settings. Stool sample is easy to obtain and since children swallow sputum, it can be used to diagnose pulmonary tuberculosis. With this background, a pilot study was planned to evaluate the accuracy of the Xpert MTB/RIF assay for the detection of MTB in stool specimens obtained from pediatric pulmonary TB patients confirmed either by gastric lavage(GL) or sputum(SP) Xpert MTB/RIF assay. In addition, the results of microscopy of stool specimen were compared with that of gastric lavage/ sputum (GL/SP) specimen by Ziehl-Neelsen (ZN) and fluorescent light-emitting diode (LED) staining.

Material and methods: A prospective study was carried out on 50 GL/SP Xpert MTB/RIF assay positive children (0-14 years). Stool specimens from these children were processed for Xpert MTB/RIF assay. The GL/SP and stool specimens were processed for ZN and Auramine O fluorescent microscopy as well.

Results: Fluorescent staining detected acid fast bacilli (AFB) in 24 GL/SP and 16 stool specimens as compared to 20 GL/SP and 10 stool specimens by ZN staining. Stool Xpert MTB/ RIF assay was positive in 29 out of 50 children. Rifampicin resistance was detected in 13 of the 50 (26%) GL/SP specimens. Of these 13 children, rifampicin resistance was detected in 7 stool specimens, rifampicin indeterminate resistance was detected in one specimen and in the remaining 5 children, M.tuberculosis was not detected in stool.

Conclusion: Stool is a good non-invasive specimen for the detection of pulmonary TB in children, especially in remote areas, where invasive techniques cannot be performed for sample collection.

Keywords: Pediatric pulmonary tuberculosis; Xpert MTB/RIF assay; diagnosis; stool.