The World Health Organization (WHO)’s Global TB Programme has revised the definition of extensively drug-resistant tuberculosis (XDR-TB). Meanwhile, pre-XDR-TB has also been defined for the first time. The new definitions for these forms of TB will assist with the precise characterization of different groups of patients with TB, while aiding in improved reporting, surveillance as well as monitoring of drug-resistant TB, worldwide.

 

The new definition of pre-XDR-TB is – TB caused by Mycobacterium tuberculosis (M. tuberculosis) strains that fulfil the definition of multidrug resistant and rifampicin-resistant TB (MDR/RR-TB) and which are also resistant to any fluoroquinolone. 

 

The updated definition of XDR-TB is – TB caused by Mycobacterium tuberculosis (M. tuberculosis) strains that fulfil the definition of MDR/RR-TB and which are also resistant to any fluoroquinolone and at least one additional Group A drug.

 

The new definitions of pre-XDR and XDR-TB applies from January 2021. The WHO estimates – around 470 000 people fall ill with MDR/RR-TB and about 180 000 die from this form of TB each year. Globally—in 105 countries with representative data—20% of the people with MDR/RR-TB also have resistance to another potent drug for the treatment of drug-resistant TB – a fluoroquinolone.

 

Source: 27 January 2021. Departmental news. Geneva. https://www.who.int/news/