What's in a name? The future of drug-resistant tuberculosis classification.

Due to a recent resurgence in tuberculosis research focused on drug development, several new antituberculosis drugs are in the pipeline, and the standard of care for tuberculosis might soon change. If new drugs replace the current first-line treatment, then existing classifications of resistance, including multidrug-resistant and extensively drug-resistant tuberculosis, might become less relevant. When much needed new drugs reach the market, a new classification system for resistance might need to be devised to describe resistance to these novel agents. Many options for such a system exist, each with its own inherent benefits and challenges. The adoption of new terminology for resistance should be guided by outcomes data from clinical trials in progress, and should be accompanied by increased support for drug susceptibility testing in developing countries to be clinically useful. Consideration of these issues now will hopefully help foster an informed approach to the classification of drug-resistant tuberculosis in the era of new drugs.