How New Regulation of Laboratory-Developed Antimicrobial Susceptibility Tests Will Affect Infectious Diseases Clinical Practice.

This article focuses on the regulatory challenges posed by the United States Food and Drug Administration’s (FDA) antimicrobial susceptibility test interpretive criteria, known as breakpoints, and their impact on antimicrobial susceptibility testing (AST) critical for addressing antimicrobial resistance (AMR). The FDA’s limited list of breakpoints restricts clearance of AST devices for many organism–antibiotic combinations, forcing laboratories to rely on legacy devices or laboratory-developed tests (LDTs) that use Clinical and Laboratory Standards Institute (CLSI) breakpoints. Proposed FDA regulation of LDTs threatens to eliminate access to essential AST for off-label organisms, potentially undermining clinical care and innovation in AST technology. The article highlights the need for collaboration among manufacturers, clinicians, laboratories, and the FDA to develop solutions that maintain AST availability and support effective AMR management.