More on Treatment Outcomes in Multidrug-Resistant Tuberculosis

In 2013, the WHO relaxed the definition of cure in MDR-TB treatment,¹ requiring only three negative cultures following the intensive phase instead of five.² Despite this, Günther et al. question the need for even 3 cultures to define successful treatment outcomes.³ Although sending mycobacterial cultures can be onerous and expensive, it pales in comparison to the actual costs of MDR-TB treatment (range: US$10,000–200,000 versus culture: US$1.63–62.01).^4,5 The authors note that 11% of their participants who had culture-converted by 6 months later relapsed. This rate might have been higher or detected sooner, had cultures been sent more regularly, as recently demonstrated in 5410 MDR-TB patients from 10 countries.⁵ Late detection of treatment failure increases the risk of amplified resistance and further transmission.

We believe that increasing lab capacity—especially in high-TB prevalence countries—would be more effective in detecting drug-resistant TB cases and managing treatment response. Rapid alternatives to culture, such as Gene Xpert^®, should also be evaluated, but until such studies are done, we believe that monitoring of therapy for MDR-TB should be more, not less stringent.