Stool-based Xpert testing for diagnosis of TB in children and critically ill adults.

We describe our approach and experience with the routine implementation of stool-based Xpert MTB/RIF Ultra (Xpert) testing for the diagnosis of childhood TB in Zambia.We conducted a method validation and subsequently introduced stool as an alternative sample for routine Xpert testing for children and critically ill adults. We reviewed the impact of stool-based Xpert testing during the first 18 months of routine implementation.The method validation showed 98.0% (95% CI 92.9-99.4) agreement between Xpert results on sputum/gastric aspirate (GA) and stool specimens. During 18 months of routine implementation, 16,210 stool samples were tested, yielding 157 TB cases in children, including five rifampicin (RIF) resistant cases, and 45 cases in critically ill adults. In children aged 0-4 years, 10,288 stool samples were tested compared to 2,459 GA samples in the same period. Childhood TB notifications and the bacteriological confirmation rate increased by 30% and 53%, respectively, in 2021 compared to 2020.The routine implementation of stool testing provided access to Xpert testing for children who could not produce sputum or have GA collected, contributing to increased bacteriological confirmation of TB in children. For critically ill adults with difficulty expectorating sputum, it facilitated a rapid test result..