Estimating the global burden of multidrug-resistant tuberculosis among prevalent cases of tuberculosis

Estimates of the multidrug-resistant tuberculosis (MDR-TB) burden are based on incomplete, infrequently updated data among a limited pool of notified or incident pulmonary TB cases.

Using World Health Organization data reported by 217 countries/territories in 2014, we calculated the MDR-TB burden among prevalent TB cases and compared these with estimates among incident and notified TB patients. We also compared treatment coverage across estimates.

Among prevalent TB patients worldwide in 2014, we estimate that 555 545 (95% credible bounds 499 340-617 391) MDR-TB cases occurred. This is 85% more than the 300 000 estimated among notified cases, and 16% more than the 480 000 among incident cases. Only 20% of MDR-TB cases among prevalent-compared to 37% of MDR-TB among notified-TB patients had access to MDR-TB treatment. Applying prior estimates, only 10% of MDR-TB cases will have successful outcomes.

Estimates based on likely-to-be-diagnosed cases of MDR-TB overlook a significant proportion of morbidity, mortality, and transmission that occur in undiagnosed, untreated, prevalent TB patients. Even though it may still likely underestimate the true disease burden, MDR-TB among patients with prevalent TB represents a closer approximation of disease burden than currently reported indicators. Progress toward elimination or control depends on policies guided by a more complete representation of the disease burden.