Meeting report of the WHO expert consultation on drug-resistant tuberculosis treatment outcome definitions

Overview

The World Health Organization (WHO) held an online consultation on the definitions of drug-resistant tuberculosis (DR-TB) treatment outcomes, on 17–19 November 2020. Organized by the WHO Global TB Programme, Geneva, Switzerland, the consultation was attended by around 70 participants, representing countries, bilateral and multilateral agencies, international organizations, nongovernmental organizations, civil society and academia.

The consultation discussed recent and potential future developments in treatment regimens for both DR-TB and drug-susceptible TB (DS-TB) and considered possible changes to the treatment outcome definitions needed for programmatic monitoring.

The specific objectives of the consultation were to discuss:

• recent developments in treatment regimens and in diagnostics for monitoring treatment of DR-TB, and to determine how these developments affect the current definitions of treatment outcomes; and
• options for changing the treatment outcome definitions, including the pros and cons of these options from various perspectives (e.g. clinical, programmatic and surveillance).

Meeting participants discussed recent developments in the areas of treatment and programming, potential future developments in these areas based on the research pipelines and suggested some overarching principles that are important and relevant to the revision of treatment outcome definitions, and suggested that the revised definitions will need to:

• be simple and, if possible, applicable to treatment of both DS-TB and DR-TB;
• be applicable to treatment regimens of different lengths;
• de-emphasize the traditional division between intensive and continuation phases;
• identify the appropriate threshold for bacteriological conversion (or reversion) in relation to the definitions of “treatment failed”, “cured” and “treatment completed”;
• consider the use of appropriate diagnostics for treatment monitoring;
• have clear parameters for defining treatment failure, based on a decision to change or stop treatment, or reliable evidence for non-response; and
• be practical for clinical and programmatic monitoring, and feasible for national TB programmes (NTPs) to implement.

Following this consultation, the WHO proposes new definitions of TB treatment outcomes that apply to assessment of treatment outcomes of all forms of TB, as summarized in the report.

Updated definitions will be included in the 2021 revision of WHO’s Definitions and reporting framework for tuberculosis. The definitions will also need to be adopted for programmatic implementation, and for use in registration and reporting to monitor progress towards ending TB.