Impact of the revised definition of extensively drug-resistant tuberculosis
Nicolas Véziris, Isabelle Bonnet, F. Morel, Lorenzo Guglielmetti, Thomas Maitre, Laure Fournier Le Ray, Wladimir Sougakoff, J. Robert, Alexandra Aubry
Abstract
Recently, the World Health Organization (WHO) has released a revised definition of extensively drug-resistant (XDR) tuberculosis (TB) that should be used for clinical and surveillance purposes starting from 1 January, 2021 [1, 2]. The previous definition of XDR-TB was TB that is resistant to any fluoroquinolone (levofloxacin and/or moxifloxacin) and to at least one of three second-line injectable drugs (SLIs: capreomycin, kanamycin and amikacin), in addition to multidrug resistance. The revised definition is: TB caused by Mycobacterium 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. WHO group A drugs currently include fluoroquinolones (levofloxacin or moxifloxacin), linezolid and bedaquiline. In addition, pre-XDR-TB is now a WHO-endorsed definition, identified as MDR/RR-TB with any fluoroquinolone resistance. Although the previous definition of XDR-TB has proved to be predictive of poor treatment outcome [3], the 2020 update appears in line with recent changes of treatment regimens given, i.e. less frequent use of SLI in favour of the potent oral drugs, bedaquiline and linezolid. Moreover, a large meta-analysis failed to show an association between mortality reduction and SLI use, whereas this association was shown for bedaquiline and linezolid [4]. In this study, we aimed to measure retrospectively the impact of the revised definition on the epidemiology of XDR-TB in France. The revised WHO definition of XDR-TB decreases the number of TB cases classified as such, and allows better focus on the most difficult to treat cases of TB <https://bit.ly/3tgaXQA> We thank all technicians working at the CNR-MyRMA for their dedication to their work.