World TB Day: WHO guidance on drug-resistant TB 'need of hour', challenging to enforce, say experts

New Delhi: The World Health Organization has issued a new guidance for diagnosing drug-resistant tuberculosis, describing it as a "novel approach" that uses the "latest technologies".

While experts believe the approach has immense potential in bolstering India's goal to eliminate tuberculosis (TB), it can be challenging in terms of making it accessible to people.

The UN health agency recommended the use of "a new class of diagnostic technologies: targeted next-generation sequencing (NGS) tests" in the third edition of "WHO Consolidated Guidelines on Tuberculosis. Module 3: Diagnosis - Rapid Diagnostics for Tuberculosis Detection", replacing the 2021 document.

The guidance was issued ahead of World Tuberculosis Day, which is observed on March 24. The date marks the day in 1882 when Dr Robert Koch announced that he had discovered the bacterium that causes TB, paving the way for diagnosing and curing this disease.

The "novel" technology -- targeted next-generation sequencing (tNGS) -- offers a higher resolution of the specific region of interest in the genome of the TB-causing bacteria, present in the patient's sample, for analysing drug resistance compared to alternative sequencing methods.

On the other hand, tests employing whole genome sequencing analyse the entire bacterial genome for drug resistance.

Using tNGS, an individual's drug-resistance profile can be comprehensively assessed compared to modern therapy regimens, and help personalise the treatment, the experts said.

"Simply put, using a single test, an individual's resistance to multiple drugs can be detected," said Dr Chhavi Gupta, an infectious disease specialist and senior consultant at Yashoda Super Speciality Hospital, Kaushambi.

The rapid diagnosis is the need of the hour for the timely treatment of active cases and breaking the transmission chain, she said.

"The inclusion of tNGS will help provide for a directed therapy to meet the needs of the patient," said Shridhar Narayanan, a pharmacologist and CEO of the Foundation for Neglected Disease Research, Bengaluru.

According to the World Health Organization (WHO), Multidrug-resistant TB (MDR-TB) is a public health crisis and a health security threat, with only about two in five people with drug-resistant TB accessing treatment globally in 2022.

Yet, despite the effectiveness of tNGS, the sophistication and complexity of the technology, coupled with the lack of manpower trained in analysing bioinformatics data, could pose a challenge for easy access to this technology in remote parts of India, Narayanan said.

Performing these tests will also require diagnostic labs to be equipped with sufficient data management and storage infrastructure, according to Chaitali Nikam, director (infexnTM) of HaystackAnalytics, a genomics-based diagnostics solutions provider.

Accompanying the guidance, the WHO also launched a new TB sequencing portal hosting more than 56,000 sequences and representing "the most advanced sequencing and phenotyping knowledge base for Mycobacterium tuberculosis (the TB-causing bacteria)".

The portal could help create a database of genetic mutations responsible for and map emerging trends in drug resistance, and eventually help design novel drug molecules for treatment, said infectious disease specialist Gupta.

A global study published in "The Lancet Infectious Diseases" journal earlier this week found that India, along with most of the world, failed to achieve WHO's End TB milestones for 2020 -- including 20 per cent reduced TB incidence and 35 per cent fewer deaths, compared to the baseline figures of 2015.

Only 17 of the 204 countries investigated were found to have met the 2020 End TB mortality milestone, with researchers citing drug resistance as an important factor for failing to meet the mortality targets.

The researchers attributed the success of the 17 countries to the "efficacious, safe, and shorter" regimen outlined in the WHO's updated recommendations on treating drug-resistant TB and issued in 2020. The recommendations came amid antibacterial resistance emerging as a major public health threat.

National social protection interventions in Moldova and Ecuador -- two of the 17 countries meeting the 2020 End TB mortality milestone -- "potentially prevented drug resistance", they said.

The study, authored by the researchers forming the Global Burden of Disease (GBD) 2021 Tuberculosis Collaborators, also found that India's TB incidence rate dropped marginally by 0.5 per cent between 2015 and 2020.

The WHO this week also released a modelling study developed with the governments of Brazil, Georgia, Kenya and South Africa and argued for increased investment in scaling up screening and preventive treatment of the bacterial infectious disease.

The results showed that for each US dollar invested, a return of up to USD 39 in terms of health and economic benefits could be reaped.