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Updated: May 22, 2025
A Tuberculosis Molecular Bacterial Load Assay TB-MBLA
Published on: April 30, 2020
Performance of a Novel Stool Quantitative Polymerase Chain Reaction Assay for Pediatric Tuberculosis Detection in
Anca Vasiliu1,2,3, Lucia Carratala-Castro4,5, Abigail Seeger1
1Baylor College of Medicine, Department of Pediatrics, Global TB Program, Houston, TX 77030, United States.
Insights
A novel stool quantitative polymerase chain reaction (qPCR) assay improves tuberculosis diagnosis in children in sub-Saharan Africa. This method offers a valuable alternative when invasive specimen collection is challenging, increasing microbiologic confirmation rates.
Area of Science:
- Pediatric infectious diseases
- Molecular diagnostics
- Global health
Background:
- Pediatric tuberculosis diagnosis is challenging due to difficulties in obtaining sputum samples.
- Current invasive methods like gastric aspiration have low diagnostic yields.
- There is a need for non-invasive, accurate diagnostic tools for childhood TB.
Purpose of the Study:
- To evaluate the diagnostic performance of a novel stool-based quantitative polymerase chain reaction (qPCR) assay.
- To assess the additive diagnostic yield of stool qPCR in children with tuberculosis in sub-Saharan Africa.
- To compare stool qPCR with existing diagnostic methods for pediatric TB.
Main Methods:
- Prospective case-control study conducted in Eswatini, Mozambique, and Tanzania (October 2020 - June 2023).
- Included 232 children diagnosed with TB and 224 healthy child controls.
- Assessed stool qPCR, stool Xpert Ultra, sputum Xpert Ultra, culture, and clinical examination.
Main Results:
- Stool sample collection was successful in 95.6% of children.
- Stool qPCR sensitivity was 35.6% against a microbiological reference standard.
- Specificity was high at 96.1% in healthy controls.
- The additive yield of stool qPCR with other tests was 8.7%.
Conclusions:
- The stool qPCR assay enhances microbiologic confirmation of tuberculosis in pediatric populations.
- This assay is particularly beneficial in high-burden settings with limited resources or diagnostic capacity.
- It provides a promising non-invasive alternative to invasive specimen collection methods for childhood TB diagnosis.
Background:
Children have paucibacillary tuberculosis and cannot provide expectorated sputum. Invasive specimen collection, by gastric aspiration or sputum induction, has a low diagnostic yield. In this study, we aimed to evaluate the diagnostic performance and additive yield of a novel stool-based assay in children diagnosed with tuberculosis in sub-Saharan Africa.
Methods:
We conducted a prospective case-control study from October 2020 to June 2023 in Eswatini, Mozambique, and Tanzania. Children under 15 years newly diagnosed with tuberculosis completed clinical examination, chest radiography, culture, sputum Xpert Ultra, stool Xpert Ultra, and stool-based quantitative polymerase chain reaction (stool qPCR) assessment. Stool qPCR sensitivity was calculated against culture, a composite microbiological reference standard, and a clinical reference standard. Specificity was calculated in a control population of healthy, TB disease-free, child household contacts.
Results:
Among 456 children, 232 were diagnosed with TB and 224 controls. Stool sample collection was achieved in 95.6% of children. The qPCR was positive in 17.2% (40/232) of clinically diagnosed participants. In the same population, test positivity was 8% (13/162) for culture, 13.4% (27/202) sputum Xpert Ultra, and 14.8% (33/223) stool Xpert Ultra. When compared to a microbiological reference standard (any positive test), the sensitivity of stool qPCR was 35.6% (21/59). Specificity in the control population was 96.1% (196/204), and the additive yield of qPCR with all tests performed was of 8.7%.
Conclusion:
This stool qPCR assay can increase the microbiologic confirmation of tuberculosis in pediatric populations from TB high-burden settings. It may be particularly useful where resource limitations or clinical capacity impedes diagnostic specimen collection via sputum induction or gastric aspiration.
