Extensively drug-resistant tuberculosis is worse than multidrug-resistant tuberculosis: different methodology and settings, same results.

The article by Kim et al. about the impact of extensively drug-resistant (XDR) tuberculosis (TB) on treatment outcomes of non–HIV-infected patients affected by multidrug-resistant (MDR) TB. Kim et al. found, with univariate analysis, that patients with XDR TB had a borderlinesignificant higher probability of treatment failure and death than did patients with MDR TB. Multivariate analysis confirmed that XDR TB is a poor independent prognostic factor for treatment failure. Two studies from our group had previously reached similar conclusions. Our first study found that patients with XDR TB in Italy and Germany, compared with patients with MDR TB, had a 5-fold increase in the risk of death (relative risk, 5.45; 95% CI, 1.95–15.27; P ! .01), required longer hospitalization, had longer treatment duration, and, for the few patients whose sputum and smear converted from positive to negative, a longer time to smear or culture conversion. The second study found that patients with XDR TB had a relative risk of 1.58 to die or have treatment failure, compared with patients with MDR TB resistant to all first-line drugs , and a relative risk of 2.61, compared with patients with MDR TB for whom susceptibility to _1 first-line drug still existed. Interestingly, the results of the studies from the 2 groups are consistent, although the definitions used were slightly different: Migliori et al. used theWorld Health Organization definitions of treatment success and failure, and Kim et al. applied the definitions proposed by Laserson et al