From the Authors:

We thank Drs. Leung and Yew for their insightful commentary on our pulmonary perspective about the challenges of estimating the burden of drug-resistant tuberculosis (1). Drs. Leung and Yew propose that current methods for drug resistance surveillance (based on the detection of resistance among incident tuberculosis cases) offer timely information both for local tuberculosis control programs and for global entities that aim to assess the worldwide burden of resistant disease. While acknowledging several of the shortcomings of incidence-based surveys that were highlighted in our perspective, Drs. Leung and Yew argue that these surveys are the most feasible approach for resistance monitoring in areas under resource constraints.

We support the view that incidence-based surveys represent a practicable approach for surveillance and are thus likely to remain important instruments for quantifying the burden of drug-resistant tuberculosis. Indeed, two of us, A. W. and M. Z., played key roles in the most recent World Health Organization report on Anti-tuberculosis Drug Resistance in the World (2), which relied heavily on such surveys. Acknowledging the utility of such studies should not preclude a discussion of what types of questions these surveys are best able to answer and in what situations they may fall short. Our perspective (1) and the related model (3) were intended to stimulate such conversation.

We strongly endorse Drs. Leung and Yew's suggestion that the surveillance for drug resistance constitutes an important public health intervention that should have objectives beyond measuring and reporting disease burden. We would expect that investment in the activities that are necessary for enhanced surveillance—improving recording and reporting mechanisms, expanding laboratory capacity, developing and implementing molecular diagnostic tools (4), and establishing sentinel sites for enhanced monitoring—would also directly support local tuberculosis control efforts. Failure to harness the additional resources necessary to accurately gauge the burden of drug resistant tuberculosis is likely to result in an underestimation of the extent of the epidemic and thus result in a persistently inadequate global public health response.