Xpert MTB/RIF assay in the diagnosis of pulmonary tuberculosis in children in tertiary care setting in South India

Abstract

Xpert MTB/RIF is recommended for the diagnosis of tuberculosis (TB) in children. We determined the performance of Xpert MTB/RIF in the diagnosis of pulmonary TB in children. The characteristics of children influencing Xpert MTB/RIF positivity were explored. Children aged <15 years with symptoms suggestive of pulmonary TB were prospectively enrolled from 2013 to 2019. Two sputum/early morning gastric aspirate specimens were collected for examination by smear (fluorescence microscopy), Xpert MTB/RIF, and culture [Mycobacteria growth indicator tube (MGIT)/Lowenstein-Jensen (LJ) medium]. Diagnostic performance of Xpert MTB/RIF was evaluated using LJ and or MGIT culture positivity as the reference standard. Sensitivity, specificity with 95% confidence interval (CI) were calculated. Stratified analysis was done; P < .05 was considered statistically significant. Of the total 1727 enrolled children, 1674 (97%) with complete results for at least one sputum/gastric aspirate sample were analyzed. The sensitivity of Xpert MTB/RIF was 68.5% in sputum and 53.6% in gastric aspirate while the specificity was 99% for both. The sensitivity compared to smear was 68.5% vs. 33.7% (P < .001) and 53.6% vs. 14.5%; (P < .001) in sputum and gastric aspirate, respectively. The sensitivity of Xpert MTB/RIF was 23.9% with decision to treat as reference standard. Xpert MTB/RIF positivity was significantly influenced by sex, age, nutritional status, chest X-ray abnormality, TB infection status, and symptoms suggestive of TB. Xpert MTB/RIF as an upfront test compared to smear improves diagnosis of pulmonary TB in children yet the sensitivity is suboptimal. Newer TB diagnostic tools with improved sensitivity is warranted in children.