Key messages
- There is limited evidence that LC-mNAATs can correctly identify pulmonary tuberculosis in children.
- Further studies are needed to assess the accuracy of LC-mNAATs among children.
Why is improving the diagnosis of pulmonary tuberculosis among children important?
Tuberculosis in children is frequently under-reported due to the difficulties associated with diagnosing the disease. Early detection and treatment of tuberculosis in children is vital for a timely and effective cure. However, recognising tuberculosis early is difficult due to its varied forms and symptoms, and challenges with producing phlegm (mucus coughed up from the lungs). In addition, bacterial levels in samples are lower than in adults. False-positive results can cause unnecessary anxiety, and children will be followed up, requiring time and resources. These children may also start tuberculosis treatment with severe side effects. False-negative results may result in missed cases, leading to the spread of the disease. Children with false-negative results may also develop severe forms of tuberculosis, leading to death due to delayed diagnosis.
What are low-complexity manual nucleic acid amplification tests for detecting tuberculosis?
One of the tests used for detecting tuberculosis is TB-LAMP (loop-mediated isothermal amplification), which belongs to a category known as low-complexity manual nucleic acid amplification tests (LC-mNAATs). These tests can be used in places with relatively simple infrastructure, similar to what is needed for sputum microscopy (microscope examination of mucus coughed up from the lungs). They are more accurate than tests with sputum or other respiratory samples, even when the bacterial count is low, and give results in a few hours. At present, there is a lack of evidence on the accuracy of the TB-LAMP test in detecting tuberculosis in children.
What did we want to find?
We wanted to find out how accurate LC-mNAATs are for detecting pulmonary tuberculosis in children presumed to have pulmonary tuberculosis and compare the accuracy with Xpert MTB/RIF Ultra and smear microscopy.
What did we do?
We searched for studies that investigated the accuracy of LC-mNAATs in detecting pulmonary tuberculosis in children and examined the results of relevant studies.
What did we find?
We included four studies (303 participants, 25 children with tuberculosis) that evaluated TB-LAMP. One study compared the accuracy of TB-LAMP and Xpert MTB/RIF Ultra, and three studies also used smear microscopy. These studies used multiple respiratory and non-respiratory specimens to detect tuberculosis. All studies used culture as the reference standard, the best available way of identifying the presence of tuberculosis.
Respiratory samples
Three studies (67 children, eight positive for tuberculosis) used respiratory samples (sputum (phlegm), bronchoalveolar lavage (fluid obtained after washing the airway and lungs), and tracheal aspirate (fluid obtained from the windpipe)). The results indicate that 60% to 100% of children with tuberculosis will be identified as positive by the TB-LAMP test, and 95% to 100% of children without tuberculosis will be identified as negative by the test.
Gastric aspirate (fluid obtained from the stomach using a tube)
Three studies used gastric aspirate samples (176 children, 14 positive for pulmonary tuberculosis). The results indicate that 64% of children with tuberculosis will be identified as positive by the TB-LAMP test, and 35% to 87% of children without tuberculosis will be identified as negative by the test.
Gastric lavage (fluid obtained from the stomach using a tube after a wash)
One study with 60 children (three positive for tuberculosis) evaluated gastric lavage. For every 1000 children tested, if 100 had tuberculosis according to culture, 135 would be TB-LAMP positive, of which 99 would have tuberculosis, and 36 would not have tuberculosis; 865 would be TB-LAMP negative, of which 864 would not have tuberculosis, and one would have tuberculosis.
Nasopharyngeal aspirate (fluid obtained from the back of the nose and throat)
One study (144 children, 12 positive for tuberculosis) evaluated nasopharyngeal aspirate. For every 1000 children tested, if 100 had tuberculosis according to culture, 71 would be TB-LAMP positive, of which 12 would have tuberculosis, and 59 would not have tuberculosis; 929 would test negative, of which 921 would not have tuberculosis, and eight would have tuberculosis.
Stool
One study evaluated stool specimens (144 children, seven positive for pulmonary tuberculosis). For every 1000 children tested, if 100 had tuberculosis according to culture, 171 would be TB-LAMP positive, of which 99 would have tuberculosis, and 72 would not have tuberculosis; 829 would test negative, of which 828 would not have tuberculosis, and one child would have tuberculosis.
What are the limitations of the evidence?
We did not find any study that used a composite reference standard (the results of different tests are combined and considered as a confirmatory test). Since culture is not the best way to determine the disease in children, our evidence is limited. The results come from four studies with a small number of children, and the findings are likely to change as more studies become available.
How up-to-date is this evidence?
The evidence is up-to-date to October 2023.
Read the full abstract
Accurate and prompt diagnosis of tuberculosis in children is challenging due to non-specific clinical presentation and the low bacillary load of samples. Low-complexity manual nucleic acid amplification tests (LC-mNAATs) such as loop-mediated isothermal amplification (TB-LAMP) are World Health Organization (WHO)-recommended rapid molecular diagnostic tests. Even in resource-limited settings, they have good diagnostic accuracy in adults.
Objectives
To determine the diagnostic accuracy of LC-mNAATs for the detection of pulmonary tuberculosis in children (< 10 years) with presumptive pulmonary tuberculosis.
Secondary objectives
1. To compare the diagnostic accuracy of LC-mNAATs and Xpert MTB/RIF Ultra for the detection of pulmonary tuberculosis in children with presumptive pulmonary tuberculosis.
2. To compare the diagnostic accuracy of LC-mNAATs and smear microscopy for detecting pulmonary tuberculosis in children when TB-LAMP is considered as a replacement test for smear microscopy.
3. To determine the diagnostic accuracy of LC-mNAATs for the detection of pulmonary tuberculosis if used as an add-on test amongst sputum smear-negative children.
4. To investigate potential sources of heterogeneity in the diagnostic accuracy of LC-mNAATs due to factors such as smear status, age, HIV status, setting, and tuberculosis burden.
Search strategy
We searched CENTRAL, MEDLINE, Embase, Science Citation Index, Biosis Previews, Global Index Medicus, SCOPUS, WHO ICTRP, and ClinicalTrials.gov on 2 October 2023 for published articles and trials in progress without language or time limits. We screened the reference lists of included articles, conference abstracts, tuberculosis reviews, and guidelines. We searched ProQuest Dissertations & Theses A&I for dissertations. We approached the Stop TB Partnership, FIND, and other experts on tuberculosis for ongoing and unpublished studies. A WHO public call was made between 30 November 2023 and 15 February 2024 for ongoing and unpublished studies from manufacturers and researchers.
Selection criteria
We included cross-sectional and cohort studies that evaluated LC-mNAATs in children (< 10 years) against microbiological or composite reference standards. Our index test was TB-LAMP, and comparator index tests were Xpert MTB/RIF Ultra and smear microscopy. The microbiological reference standard included automated liquid culture, solid culture, or a combination of both methods. We considered only design-locked, marketed technologies.
Data collection and analysis
Four review authors, in pairs, independently screened titles and abstracts and assessed the full texts of potentially eligible articles. A fifth review author resolved any disagreements. We tailored and applied the QUADAS-2 and QUADAS-C tools to assess the risk of bias and applicability. Six review authors, in three pairs, extracted data and performed methodological quality assessment. A seventh review author resolved any disagreements. We contacted the primary study authors for missing data. We assessed the certainty of evidence using the GRADEpro GDT online tool.
Main results
We included four eligible studies (303 participants). Three studies took place in low- and middle-income countries, with two studies from countries with a high tuberculosis burden. All four studies assessed different respiratory and non-respiratory specimen types and evaluated TB-LAMP against the microbiological reference standard.
We judged one study to have an unclear risk of bias in two domains of QUADAS-2. The risk of bias was low for most of the studies. One study recruited inpatients from tertiary hospitals, causing high applicability concerns.
Three studies (67 children, including eight with pulmonary tuberculosis) evaluated respiratory samples (sputum, broncho-alveolar lavage, and tracheal aspirate). The sensitivities were between 60% and 100%, and the specificities were between 95% and 100% (very low-certainty (sensitivity) and low-certainty (specificity) evidence). Three studies (176 participants, including 14 children with pulmonary tuberculosis) used gastric aspirate; the sensitivity was not estimable in two studies, and was 64% in the third study. The specificities were between 93% and 100%. The sensitivity was 100% (95% confidence interval (CI) 29 to 100), and the specificity was 96% (95% CI 88 to 100) in gastric lavage from one study. One study (144 participants, 12 children with pulmonary tuberculosis) assessed diagnostic accuracy using nasopharyngeal aspirate. The sensitivity was 58% (95% CI 28 to 85), and the specificity was 94% (95% CI 88 to 97). The same study (seven children with pulmonary tuberculosis) also evaluated stool specimens, and the sensitivity and specificity were 100% (95% CI 59 to 100) and 92% (95% CI 86 to 96), respectively. We did not perform a meta-analysis due to limited data.
Interpretation of the results
Respiratory samples
For every 1000 children tested, if 100 had tuberculosis according to culture, 60 to 100 with tuberculosis would be identified as positive by the TB-LAMP. Of the 900 children without tuberculosis, 855 to 900 would be identified as negative by the test.
Gastric aspirate
For every 1000 children tested, if 100 had tuberculosis according to culture, 64 with tuberculosis would be identified as positive by the TB-LAMP. Of the 900 children without tuberculosis, 837 to 900 would be identified as negative by the test.
Gastric lavage
For every 1000 children tested, if 100 had tuberculosis according to culture, 135 would be TB-LAMP positive, of which 100 would have tuberculosis (true positives), and 35 would not have tuberculosis (false positives); 865 would be TB-LAMP negative, of which 864 would not have tuberculosis (true negatives), and one would have tuberculosis (false negatives).
Nasopharyngeal aspirate
For every 1000 children tested, if 100 had tuberculosis according to culture, 112 would be TB-LAMP positives, of which 58 would have tuberculosis (true positives), and 54 would not have tuberculosis (false positives); 888 would test negative, of which 846 would not have tuberculosis (true negatives), and 42 would have tuberculosis (false negatives).
Stool
For every 1000 children tested, if 100 had tuberculosis according to culture, 171 would be TB-LAMP positive, of which 99 would have tuberculosis (true positives), and 72 would not have tuberculosis (false positives); 829 would test negative, of which 828 would not have tuberculosis (true negatives) and one child would have tuberculosis (false negative).
Authors' conclusions
Evidence on the diagnostic accuracy of LC-mNAATs for the detection of pulmonary tuberculosis in children is limited due to few and small studies. Adequately powered studies evaluating LC-mNAATs in children are needed.
