Newly published guidance enables advances in testing for TB and drug resistance
FIND has contributed to two major documents recently published by the WHO that represent major advances in testing for tuberculosis (TB) and drug resistance: the WHO consolidated guidelines on tuberculosis; module 3: diagnosis – rapid diagnostics for tuberculosis detection 2021 update and Catalogue of mutations in Mycobacterium tuberculosis complex and their association with drug resistance.
There are over half a million cases of drug-resistant TB each year. Drug-resistant TB develops when the long, complex, decades-old TB drug regimen is improperly administered, or when people with TB stop taking their medicines before the disease has been fully eradicated from their body. Recent treatment advances – including the positive results just released from TB Alliance’s ZeNix trial of the optimized bedaquiline, pretomanid and linezolid (BPaL) regimen – are already making a huge impact, but they rely on patients starting on treatment as soon as possible. This depends on rapid diagnosis, which is why the WHO End TB Strategy requires universal drug susceptibility testing and treatment of all people with TB.
Consolidated guidelines on TB
The updated guidance includes WHO endorsement of three new nucleic acid amplification test (NAAT) classes. This includes the Xpert® MTB/XDR test, for which FIND provided clinical trial evidence to WHO as part of the WHO assessment. This test can enable clinicians to quickly prescribe treatment regimens for multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB). The guidelines are accompanied by an operational handbook to facilitate rapid implementation and roll out of rapid molecular tests by national TB programmes, ministries of health and technical partners.
Morten Ruhwald, Head of TB at FIND, said: “With the Xpert® MDR/XDR test we now have a rapid molecular diagnostic for drug resistance to key TB drugs, to guide test-and-treat approaches and support roll-out of the optimized BPaL treatment regimen. This is a major step forward for patients, and critical progress towards the End TB targets.”
Catalogue of mutations in M. tb
Cataloging the mutations of the TB bacterium and the association of these mutations with drug resistance means the community now has a reference standard for understanding the mutations that confer resistance to all first-line and most second-line drugs. The work is a collation and analysis of the largest collection of TB isolates from all over the world to date. As the “list of truth” for TB drug resistance, it will enable design and standardized interpretation of results of molecular drug susceptibility tests, including next-generation sequencing-based tests, especially for newer drugs and drug regimens.
Developed by partners including FIND, CRyPTIC, Oxford University, Ospedale San Raffaele Milan, the Stop TB Partnership New Diagnostics Working Group, technical experts and WHO – and funded by Unitaid as part of the FIND Seq&Treat project – it is a critical resource for TB molecular diagnostic developers, researchers, and clinicians, as well as national TB programmes.
Anita Suresh, Head of Sequencing at FIND, said: “This is the first time WHO has endorsed a list of mutations for not only developing new tests but also interpreting existing tests. This work sets a standard for the statistical analysis and interpretation of resistance conferring mutations – not just for TB but any sequence-based diagnostics, which has implications for tackling antimicrobial resistance in numerous diseases.”
 World Health Organization. Global Tuberculosis Report 2020. who.int/publications/i/item/9789240013131 (accessed 20 July 2021).
 TB Alliance. New trial results show effectiveness of BPaL regimen for highly drug-resistant TB can be maintained with reduced dosing of linezolid. https://www.tballiance.org.za/news/zenix-press-release-english (accessed 20 July 2021).
More information: https://www.finddx.org/newsroom/pr-21jul21/