New Delhi: One of the top 10 causes of death worldwide, tuberculosis (TB) clocks up approximately 2.8 million cases and nearly half a million deaths on an annual basis in India.
TB is an infectious, airborne disease mainly affecting the lungs and is caused by the bacterium Mycobacterium tuberculosis.
For its diagnosis, many countries still rely on a long-used method called sputum smear microscopy. Trained laboratory technicians look at sputum samples under a microscope to see if TB bacteria are present. Microscopy detects only half the number of TB cases and cannot detect drug-resistance.
However since 2010, following the recommendation of the World Health Organisation (WHO), the use of the rapid test Xpert MTB/RIF® has expanded substantially.
Through this test, diagnosis can be made within 2 hours and the test is now recommended by WHO as the initial diagnostic test in all persons with signs and symptoms of TB.
But, now, scientists have come up with the first rapid blood test that can diagnose tuberculosis and measure the severity of the deadly infection within a few hours, an advance that may help combat the worldwide epidemic.
Despite USD 6.6 billion spent for international tuberculosis (TB) care and prevention efforts, TB remains a major risk to human health, particularly for the developing world and people with HIV infections.
Making matters worse, TB bacteria can lurk dormant in a person's lung tissue, often for decades, before spontaneously producing full-blown TB disease that can then spread to others.
Currently, the World Health Organisation (WHO) estimates that up to one-third of the world's population may have such dormant TB infections.
"In the current frontlines of TB testing, coughed-up sputum, blood culture tests, invasive lung and lymph biopsies, or spinal taps are the only way to diagnose TB," said Tony Hu, researcher at Arizona State University in the US.
"The results can give false negatives, and these tests are further constrained because they can take days to weeks to get the results," said Hu.
According to the WHO's most recent report in 2016, an estimated 10 million people worldwide still develop TB each year, resulting in almost two million deaths.
TB remains a worldwide epidemic due to the lack of an effective TB vaccine, the rise in drug-resistant strains and the relatively poor performance of available TB diagnostics.
The new blood-based TB test outperforms all others currently on the market and takes just hours to complete.
This is critical since effective TB control requires that patients start treatment as soon as possible to reduce the risk of spreading TB.
This test also holds promise for rapid assessment of TB treatment, an important factor in reducing the development and spread of drug-resistant TB strains, researchers said.
"We are particularly excited about the ability of our high-throughput assay to provide rapid quantitative results that can be used to monitor treatment effects, which will give physicians the ability to better treat worldwide TB infections," said Hu.
"Furthermore, our technology can be used with standard clinical instruments found in hospitals worldwide," he said.
Current TB assays often demonstrate reduced performance with HIV-positive TB patients or those with TB infections in non-lung tissues, and these patients can require tissue biopsies for diagnosis.
The new assay detected lung- and non-lung-resident TB cases with similar sensitivity (about 92 percent) regardless of patient HIV status, and revealed good specificity to distinguish patients with related disease cases (latent TB and nontuberculous mycobacterial infections; 87 and 91 percent, respectively) and healthy subjects (100 percent).
The strategy used to generate this assay may also be adaptable to other infectious diseases, researchers said.
(With PTI inputs)
