Researchers have developed a faster and ultrasensitive blood-based test to accurately diagnose active tuberculosis (ATB), that could be used to help millions of people infected with the deadly disease.
The test developed by researchers, including those from The Broad Institute of Harvard and MIT in the US, analyses a "signature" of the combined levels of four proteins and an anti-TB antibody in blood samples to identify patients who are likely to have active ATB, and require advanced diagnostics and treatment.
It can be configured into a point-of-care test that costs only USD 2 and gives results in about 30 minutes, lowering the barrier to care in low-resource settings and potentially saving millions of lives, according to the research published in the journal Science Translational Medicine.
Over 10 million people around the world have ATB, and every year more than a million die from it, the researchers said.
The majority of patients live in low-resource countries where diagnosing ATB is especially challenging -- newer tests require expensive lab equipment that is frequently not available, they said.
"Our test demonstrated 86 per cent sensitivity and 69 per cent specificity, which are very close to the WHO's minimum requirements of 90 per cent sensitivity and 70 per cent specificity for an effective TB triage test," said Rushdy Ahmad, a former Research Scientist at the Broad Institute.
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"It also effectively identified the ATB signature in patient samples from three different continents, meaning it can detect many strains of the pathogen, and in both HIV-positive and HIV-negative samples, making it widely applicable to most ATB patients," Ahmad said.
The research team set out to create their blood-based test by identifying a signature set of biomarkers in patients' blood that consistently indicated a high likelihood of ATB, then developing an easily deployable assay that could detect that signature.
The researchers first measured the levels of 47 different blood proteins in about 400 samples taken from people in Tanzania and the Philippines who had been diagnosed with either ATB or a condition other than TB (OTB) using a traditional microbiologic assessment.
To improve the test's ability to detect very low concentrations of the four proteins, they developed an ultrasensitive immunoassay that enabled effective measurement of protein levels using as little as a drop of blood from a fingerprick.
For the second phase of the study, the research team validated their algorithm by testing its ability to identify ATB in a different set of 317 samples taken from patients in Vietnam, South Africa, and Peru.