Which standard is commonly used to set dose-specific breakpoints and quality-control ranges for many organisms in the United States?

• A. EUCAST
• B. FDA
• C. CLSI
• D. WHO

Answer: (C)

Interpreting antimicrobial susceptibility tests depends on standardized breakpoints that translate an organism’s MIC into clinical categories and on quality-control ranges that ensure the testing method is performing correctly. In the United States, the organization that develops and maintains these interpretive criteria and QC ranges is CLSI (Clinical and Laboratory Standards Institute). They publish guidelines for how to perform testing and provide breakpoints for many drug–organism combinations, including dose-specific interpretations where applicable. These breakpoints reflect what drug exposure can achieve in patients and guide which therapies are likely to be effective. The quality-control ranges specify the expected results for reference strains to verify that reagents, instruments, and procedures are working properly. While other groups provide guidelines, CLSI standards are the primary basis for setting these breakpoints and QC values in US clinical laboratories.