New blood test to detect TB in kids

PTI London | Updated on September 01, 2014 Published on September 01, 2014

Researchers have developed a new reliable and highly specific blood test to diagnose tuberculosis in children within 24 hours.

The newly developed test (TAM-TB assay) is the first reliable immunodiagnostic assay to detect active tuberculosis in children, researchers said.

The test features excellent specificity, a similar sensitivity as culture tests in combination with speed of a blood test, they said.

Tuberculosis in children is a serious public health problem especially in low-resource countries. About one million children per year develop tuberculosis worldwide.

Unfortunately, the diagnosis of paediatric TB poses a major challenge. TB symptoms in children are often non-specific and similar to those of common paediatric illnesses, including pneumonia and malnutrition. Further, obtaining adequate respiratory specimens for direct mycobacterial confirmation is problematic.

Consequently, there is an urgent need for a more precise, rapid and affordable diagnostic test for childhood tuberculosis. The new TAM-TB assay is a sputum-independent blood test.

It makes use of an immunological phenomenon during tuberculosis disease: During an active infection, the expression of CD27 - a surface marker expressed on mycobacteria specific CD4+ T cells - is lost.

Using standard intracellular cytokine staining procedures and polychromatic flow cytometry, the test result is available within 24 hours after blood sampling.

The new test was assessed in tuberculosis endemic regions in Tanzania at the Ifakara Health Institute and the National Institute for Medical Research (NIMR) Mbeya Medical Research Centre.

Sputum and blood samples were obtained from children with tuberculosis symptoms to compare the performance of the new assay with culture tests.

For the assessment of the diagnostic performance of the new test, the children were assigned to standardised clinical case classifications based on microbiological and clinical findings. The test proved to have a good sensitivity and excellent specificity.

“This rapid and reliable test has the great potential to significantly improve the diagnosis of active tuberculosis in children,” said TB CHILD Programme Manager Klaus Reither from the Swiss Tropical and Public Health Institute (Swiss TPH), who coordinated the study.

The study has been published in the journal Lancet Infectious Diseases.

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Published on September 01, 2014
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