Reply from Kirn and Sharp to Brecher, ‘EUCAST and CLSI Point-Counterpoint on Susceptibility Breakpoints: Do Two “I Agree”s Miss the Point?’

REPLY

Undoubtedly, complete harmonization of antimicrobial susceptibility breakpoints and categorical interpretations worldwide would mean less confusion for laboratorians and doctors and would also simplify global surveillance efforts that rely upon data generated as part of routine health care practices. However, significant barriers to achieving this goal exist, including the following:

• 1. Identification of a clear process for working together. At this time, the EUCAST chair serves on the CLSI antimicrobial susceptibility subcommittee by invitation as an advisor, yet no reciprocal relationship exists that gives CLSI leadership a voice in the EUCAST process.

• 2. Differences in susceptibility testing methods. For example, EUCAST recommends the use of some disks with different drug concentrations and different medium types than those recommended by CLSI.

• 3. Differences in requirements and/or influence by regulatory agencies in the United States versus Europe.

• 4. The tremendous amount of work required to harmonize. Changing breakpoints and testing methodologies is a lengthy and often costly process that requires the collection and review of large amounts of data, followed by extensive deliberation to reach consensus.

Despite these challenges, steps toward harmonization have already been made between these two standard setting organizations. For example, both groups are currently engaged in a Transatlantic Task Force for Antimicrobial Resistance (TATFAR) working group on harmonization and have identified first priorities for harmonization. More collaborative work by both will no doubt continue this process.