Establishment and Use of Epidemiological Cutoff Values for Molds and Yeasts by Use of the Clinical and Laboratory Standards Institute M57 Standard

Breakpoints are used to predict whether an antifungal agent will be clinically effective against a particular fungal isolate. They are based on a combination of MIC values, pharmacokinetic/pharmacodynamic values, and clinical outcome data. For many fungus-antifungal combinations, these data might never be available. For these combinations, epidemiological cutoff values (ECVs) provide a methodology for categorizing isolates as either wild type (WT) or non-WT. In this review, we define ECVs, explain how they are generated using the CLSI methodology in standard M57, and describe how they can be used in clinical practice.