Smear microscopy needs to be replaced with molecular testing for tuberculosis: expert

On how countries can make the switch from microscopy to molecular diagnostics, Pai said, “During the Covid-19 pandemic, countries expanded molecular testing capacity to unprecedented levels. This infrastructure should now be repurposed to diagnose TB and other infectious diseases.”

“Historically and even today, India is still reliant on smear microscopy. However, it has limitations, such as low sensitivity and an inability to detect drug resistance. On the other hand, molecular testing is more accurate,” said the TB expert.

“TB is a priority for the Prime Minister and the domestic budget has increased in the past few years. Also, India now has its own indigenous molecular platform (TrueNAT by Molbio Diagnostics). During Covid-19, India worked hard to lower the cost of PCR reagents via C-CAMP. So, I see no reason why India cannot replace microscopy with molecular testing in 2023,” said the professor.

In 2021, TB killed an estimated 1.6 million people with most deaths occurring in low and middle-income countries. “If detected early, screened for drug resistance, and fully treated with appropriate short-course regimens, TB can be cured. But globally, diagnosis is the weakest link in the TB cascade with only one in two people with drug-sensitive TB completing all the steps of the continuum of care,” Professor Pai , Puneet Dewan, senior programme officer, Bill and Melinda Gates Foundation, and Dr. Soumya Swaminathan, chairperson of M S Swaminathan Research Foundation have said in their comments in Nature Microbiology.

Although shorter drug regimens are available to treat all forms of TB, none of these regimens are likely to realise their potential public health impact until diagnosis is improved. According to Dr Pai, “If we cannot find TB, we cannot treat TB. And if we cannot treat TB, we cannot end TB.”

Universal access to tuberculosis diagnostics will result in better health for all and reduce the unacceptably high mortality due to this curable and preventable disease, the WHO said as it released for the first time the WHO standard: Universal access to rapid TB diagnostics in April.

The new standard recommends that “in all facilities in all districts, the TB diagnostic algorithm requires the use of a WHO-recommended diagnostic as the initial diagnostic test for all patients with presumed TB, including people living with HIV, children and individuals with extrapulmonary TB,” said professor Pai.

Earlier, professor Kelly Chibale from the Drug Discovery and Treatment Centre, University of Cape Town, South Africa spoke of the collaborative efforts of researchers from academia, not-for-profit R and D organisations and industry that resulted in the continuous growth of TB drug discovery and development pipeline.