Centrifugation Versus Centrifugation-Free Stool Processing: Can the Simple One-Step Method Reliably Diagnose Pediatric Pulmonary Tuberculosis Using Xpert MTB/RIF Ultra?

TL;DR

This study compares two methods for processing stool samples to detect pediatric pulmonary tuberculosis using Xpert MTB/RIF Ultra, finding that one method misses many cases.

Contribution

The study evaluates the diagnostic reliability of a centrifugation-free method versus centrifugation-based processing for stool-based TB testing in children.

Findings

The SOS method detected 50.8% of CBP-positive samples but missed 85.1% of trace-detected cases.

The SOS method had 100% negative agreement with the CBP method.

CBP is recommended for broader TB detection in children due to SOS's limitations in trace-burden cases.

Abstract

Background/Objectives: Stool-based GeneXpert testing has become a useful approach for diagnosing pediatric pulmonary tuberculosis (PTB). This study compared two stool-processing methods, centrifugation-based processing (CBP) and simple one-step (SOS), for detecting PTB in children using Xpert MTB/RIF Ultra (Ultra). Methods: Children with presumptive PTB were screened cross-sectionally, and stool samples were collected and tested with Ultra using the CBP method from March 2022 to December 2024 across seven divisions of Bangladesh. A subset of stool samples (n = 281) that tested positive (n = 191) and negative (n = 90) by the CBP method were re-tested again with the same sample by Ultra using the SOS method. The results of the Ultra with SOS-processed stool were compared with the CBP method to evaluate overall agreement and detection efficiency across different bacterial burdens. Results: The SOS method detected 97 of 191 CBP-positive samples, resulting in a positive percentage agreement of 50.8% (95% CI: 43.5–58.1). All 90 Ultra-negative stool were also negative by the SOS method, yielding a negative percentage agreement of 100% (95% CI: 96.0–100.0). Overall agreement between the methods was 66.6% (Kappa: 0.398). The SOS method detected 100% of high- (4/4) and medium- (7/7), 97.3% (36/37) of low-, and 83.3% (35/42) of very-low-bacterial-burden samples, but only 14.9% (15/101) of the trace-detected samples that were identified by the CBP method. Conclusions: Stool testing with Ultra using the SOS processing method missed a significant number of the most prevalent form of child TB—the ‘trace-detected’ category identified by the CBP method. For increased detection of childhood TB nationwide, the national program should prioritize the use of Ultra on stool samples processed by the CBP method.

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