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Updated: Dec 21, 2025
Diagnosing Pulmonary Tuberculosis with the Xpert MTB/RIF Test
Published on: April 9, 2012
Xpert Ultra Assay on Stool to Diagnose Pulmonary Tuberculosis in Children
Senjuti Kabir1, S M Mazidur Rahman1, Shakil Ahmed2
1Programme on Emerging Infections, Infectious Diseases Division, icddr,b, Dhaka, Bangladesh.
Insights
The Xpert Ultra assay on stool shows promise for diagnosing childhood pulmonary tuberculosis (PTB), offering improved sensitivity compared to Xpert. However, its specificity is lower, and a high rate of "trace calls" necessitates further research for effective management strategies.
Area of Science:
- Pediatric infectious diseases
- Microbiology
- Diagnostic assay development
Background:
- The World Health Organization recommends Xpert MTB/RIF Ultra for diagnosing pulmonary tuberculosis (PTB).
- Stool is a potential alternative specimen for PTB diagnosis in children, but its utility with Xpert Ultra is unestablished.
- Assessing the diagnostic performance of Xpert Ultra on stool specimens in children is crucial.
Purpose of the Study:
- To evaluate the diagnostic accuracy of the Xpert MTB/RIF Ultra assay using stool specimens for detecting pulmonary tuberculosis (PTB) in children.
- To compare the performance of Xpert Ultra on stool with the standard Xpert assay on stool.
Main Methods:
- A cross-sectional study was conducted in 4 tertiary care hospitals in Dhaka, Bangladesh.
- Children under 15 years with presumptive PTB provided induced sputum and stool specimens.
- Specimens were tested using culture, Xpert, and Xpert Ultra assays.
Main Results:
- Xpert Ultra on stool demonstrated a sensitivity of 58.6% and specificity of 88.1% against sputum-confirmed PTB.
- Xpert on stool showed lower sensitivity (37.9%) but 100% specificity.
- Among bacteriologically confirmed cases, Xpert Ultra on stool yielded positive results in 83.3% of children, with 80% classified as 'trace call'.
Conclusions:
- Xpert Ultra on stool offers enhanced sensitivity for pediatric PTB diagnosis compared to Xpert on stool.
- Lower specificity and a high frequency of 'trace calls' with Xpert Ultra on stool require further investigation.
- Longitudinal studies are needed to understand the clinical implications of 'trace calls' for managing childhood PTB.
Background:
The World Health Organization recommends the Xpert MTB/RIF Ultra assay for diagnosing pulmonary tuberculosis (PTB) in children. Though stool is a potential alternative to respiratory specimens among children, the diagnostic performance of Xpert Ultra on stool is unknown. Thus, we assessed the diagnostic performance of Xpert Ultra on stool to diagnose PTB in children.
Methods:
We conducted a cross-sectional study among consecutively recruited children (< 15 years of age) with presumptive PTB admitted in 4 tertiary care hospitals in Dhaka, Bangladesh, between January 2018 and April 2019. Single induced sputum and stool specimens were subjected to culture, Xpert, and Xpert Ultra. We considered children as bacteriologically confirmed on induced sputum if any test performed on induced sputum was positive for Mycobacterium tuberculosis and bacteriologically confirmed if M. tuberculosis was detected on either induced sputum or stool.
Results:
Of 447 children, 29 (6.5%) were bacteriologically confirmed on induced sputum and 72 (16.1%) were bacteriologically confirmed. With "bacteriologically confirmed on induced sputum" as a reference, the sensitivity and specificity of Xpert Ultra on stool were 58.6% and 88.1%, respectively. Xpert on stool had sensitivity and specificity of 37.9% and 100.0%, respectively. Among bacteriologically confirmed children, Xpert Ultra on stool was positive in 60 (83.3%), of whom 48 (80.0%) had "trace call."
Conclusions:
In children, Xpert Ultra on stool has better sensitivity but lesser specificity than Xpert. A high proportion of Xpert Ultra assays positive on stool had trace call. Future longitudinal studies on clinical evolution are required to provide insight on the management of children with trace call.
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