Podcast: Xpert Ultra for diagnosing tuberculosis and rifampicin resistance in children

Most Cochrane Reviews look at the effects of interventions on health, but a growing number provide evidence on how to diagnose a disease. In September 2022, one of these diagnostic test accuracy reviews was updated for a test used to detect tuberculosis in children. The lead author, Alex Kay (left), and co-author, Tara Ness, from the Texas Children’s Hospital in Houston in the USA, tell us about the importance of the review and its latest findings in this podcast.

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Mike: Hello, I'm Mike Clarke, podcast editor for the Cochrane Library. Most Cochrane Reviews look at the effects of interventions on health, but a growing number provide evidence on how to diagnose a disease' In September 2022, one of these diagnostic test accuracy reviews was updated for a test used to detect tuberculosis in children' The lead author, Alex Kay, and co-author, Tara Ness, from the Texas Children’s Hospital in Houston in the USA, tell us about the importance of the review and its latest findings in this podcast'

Alex: Every year, an estimated one million children and young adolescents become ill with tuberculosis, and around 226,000 die from the disease' Tuberculosis is caused by the bacterium Mycobacterium tuberculosis and mostly affects the lungs, as pulmonary tuberculosis' Signs and symptoms of pulmonary tuberculosis include cough, fever, night sweats and weight loss' When detected early and treated effectively, tuberculosis is largely curable' Xpert Ultra, a World Health Organization‐recommended rapid test that detects tuberculosis in adults and children with tuberculosis symptoms may be able to accurately diagnose tuberculosis in children and increase early diagnosis'

Tara: To investigate this, we looked at the accuracy of Xpert Ultra in children with symptoms of tuberculosis, using sputum, gastric aspirate stool, and nasopharyngeal aspirate specimens, for diagnosing pulmonary tuberculosis and we have found evidence to support its use' We evaluated multiple specimen types because collection of gastric specimens and sputum can be invasive and are complicated procedures in children, but stool is an easily obtainable specimen'

Alex: We included 14 studies for pulmonary tuberculosis and analysed 335 data sets that contained a total of around 26,000 participants' In our analysis, we were able to calculate the averages for the sensitivity of Xpert Ultra, which is the proportion of children who will be correctly diagnosed as having pulmonary tuberculosis, also called true positives; and the specificity, which is the proportion of true negatives, namely those who are correctly identified as not having the disease' 

Tara: Turning to the results, there were five studies for sputum specimens and Xpert had a sensitivity of 75'3% and a specificity of 97'1%' For gastric specimens, there were seven studies, with a sensitivity of 70'4% and a specificity of 94'1%; and for stool specimens, the six studies gave a sensitivity of 56'1% and a specificity of 94'1%' Our certainty in this evidence for test sensitivity was high for sputum and moderate for gastric aspirates and stool' We also looked at nasopharyngeal aspirate specimens; for which there were four studies with a sensitivity of 43'7% and a specificity of 97'5%, but our certainty in this evidence is very low'

Alex: In summary, we found that Xpert Ultra sensitivity varied by specimen type, with sputum having the highest sensitivity, followed by gastric aspirate and stool' Nasopharyngeal aspirate had the lowest sensitivity' Across all the types of samples, Xpert Ultra specificity was high, suggesting that it will miss few cases of pulmonary tuberculosis' Therefore, our findings provide support for the use of Xpert Ultra as an initial rapid molecular diagnostic in children being evaluated for tuberculosis'

Mike: Thanks Alex and Tara' If you would like to learn more about this test for pulmonary tuberculosis in children, the full review is available free at Cochrane Library dot com with a simple search for 'Xpert ultra assay for tuberculosis in children’'

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