Impact of the revised definition of extensively drug resistant tuberculosis.

Recently, the World Health Organization (WHO) has released a revised definition of extensively drug-resistant tuberculosis (XDR-TB) that should be used for clinical and surveillance purposes starting from January 1st, 2021 [1, 2]. The previous definition of XDR-TB TB was TB that is resistant to any fluoroquinolone (levofloxacin and/or moxifloxacin) and to at least one of three second-line injectable drugs (SLI, 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 favor of 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. Footnotes This manuscript has recently been accepted for publication in the European Respiratory Journal . It is published here in its accepted form prior to copyediting and typesetting by our production team. After these production processes are complete and the authors have approved the resulting proofs, the article will move to the latest issue of the ERJ online. Please open or download the PDF to view this article. Conflict of interest: That the national reference centre receives an annual grant from SantePublique France; that the laboratory in which they work has received a research grant from Janssen for a study on bedaquiline.