To the

Editors: In their retrospective study, HWANG et al. [1] found the prevalence of extensively drug-resistant tuberculosis (XDR-TB) to be 21 % amongst multidrug-resistant (MDR) patients. However, the available literature indicates that it is around 10 % [2]. The XDR-TB data of HWANG et al. [1] was based on the drug susceptibility test for ofloxacin only; it was not performed for other commonly used quinolones. The data would have been higher if drug susceptibility to other commonly used quinolones could have been carried out. The proportion of XDR-TB amongst these patients would therefore have been higher. XDR-TB has been reported with high HIV prevalence [3]. It would therefore have been more appropriate if HWANG et al. [1] had discussed the correlation with HIV and TB co-infection i