November 14, 2019
2 min read

Rapid triage test distinguishes between active TB and TB-like diseases in adults

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David R. Walt, PhD
David R. Walt

A new point-of-care rapid triage test for human blood samples can differentiate active cases of tuberculosis from TB-like disease in adults in less than an hour, according to data published in Science Translational Medicine.

“There is a tremendous need to identify individuals who require TB treatment. Present technologies for diagnosing TB are expensive,” David R. Walt, PhD, professor in the department of pathology at Brigham and Women’s Hospital and the Wyss Institute for Biologically Inspired Engineering at Harvard University, told Infectious Disease News. “Our goal was to develop a triage test to identify at-risk individuals and eliminate those individuals who did not need further testing. In this way, we hoped to rapidly and cost-effectively identify individuals who required confirmative testing at significantly lower cost than if they all had to undergo primary testing.”

In the study, Walt and colleagues explained their hypothesis: “that a blood protein-based host response signature for active TB could distinguish it from other TB-like disease in adult patients with persistent cough,” providing the foundation for a point-of-care test for active TB.

They recruited 406 participants with symptoms suggestive of pulmonary TB from two sites in Tanzania and one in the Philippines and created an ultrasensitive immunoassay (Simoa) that screens for four blood proteins — three interleukin proteins (6, 8 and 18) and vascular endothelial growth factorthat could distinguish between active TB and TB-like diseases in blood samples.

They validated the model in a cohort of 317 subjects from Peru, South Africa and Vietnam, which showed that the test distinguished active TB from other TB-like diseases with a sensitivity of 80% sensitivity and specificity of 65%. According to the study, when the added host antibodies against TB antigen Ag85B to the panel, performance improved to 86% sensitivity and 69% specificity. Walt said this enabled them to get very close to meeting the WHO requirements for a triage test.

He added that although the test may be less accurate than a full diagnostic test, it provides a quicker result and good guidance as to whether other tests are necessary.

“These performance characteristics make it potentially of great use in the developing world where the availability of the other tests is limited to well-resourced hospitals and clinics,” he said. “An ultrasensitive protein-based test can provide a quick and inexpensive test for determining whether someone has a high probability of having an active tuberculosis infection. This test can be used as a tool to manage the disease in regions where there is a high prevalence of disease and where resources for diagnostic testing are limited.” – by Caitlyn Stulpin

Disclosure: Walt reports holding a financial interest in Quanterix Corporation, which develops an ultrasensitive digital immunoassay platform, and to being an inventor of the Simoa technology and a founder of the company, for which he serves on the board of directors. Please see the study for all other authors’ relevant financial disclosures.