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FDA Makes Up-to-Date Susceptibility Test Interpretive Criteria (Breakpoint) Resources Available Online


Published by the Clinical and Laboratory Standards Institute 

The US Food & Drug Administration (FDA) has taken an important step to improve public health by creating a website to make critical updates regarding antimicrobial drugs available to health care professionals. This information helps laboratories report the most current information to health care providers about what type of infection a patient has and what the most effective treatment will be. The website provides information on the most up-to-date Susceptibility Test Interpretive Criteria (STIC), also known as breakpoints. Breakpoints help determine whether a specific bacteria or fungi are susceptible to (ie, will respond to treatment with) antibacterial or antifungal drugs. According to the FDA, “This approach is intended to aid health care professionals in making more informed prescribing decisions that will both benefit their patients and prevent the spread of resistant bacteria.”

Providing up-to-date breakpoints is an important step in improving public health by addressing the timely issue of antimicrobial resistance. Antimicrobial resistance occurs when bacteria and fungi change over time to become less susceptible to drugs that once were effective. When this occurs, breakpoints may need to be updated. Providing current breakpoints helps health care providers treat patients with the correct drug. Antimicrobial resistance is one of the most serious global public health concerns today.

The new approach is an important improvement to the previous method of reporting breakpoints, in which drug manufacturers updated drug labeling with new breakpoint information, which had to be approved by the FDA on a case by case basis. This process created a delay in getting important breakpoint information to health care professionals. Drug labeling will now direct the reader to the FDA’s online information.

The FDA will leverage the work done by standards development organizations that develop breakpoints, such as Clinical and Laboratory Standards Institute (CLSI), and recognize those breakpoints when the FDA agrees that they are appropriate. The FDA currently recognizes seven CLSI standards, either in whole or part, which contain standardized reference methods that measure the susceptibility of bacteria and fungi to antimicrobial agents. Susceptibility testing breakpoints are established by the Subcommittee on Antimicrobial Susceptibility Testing after comprehensive review of available relevant data. The Subcommittee comprises representatives from the health care professions, government, and industry, including microbiology laboratories, government agencies, health care providers and educators, and pharmaceutical and diagnostic microbiology industries. Using the CLSI voluntary consensus process, the Subcommittee develops standards that promote accurate antimicrobial susceptibility testing and appropriate reporting. You can find out more about the Subcommittee on Antimicrobial Susceptibility testing at clsi.org/meetings/ast/.

The FDA provides an easily accessible list of recognized standards for antibacterial STIC and antifungal STIC.


For more information, contact Patrick McGinn at Clinical and Laboratory Standards Institute (CLSI) at pmcginn@clsi.org or +1.484.588.5933. 

CLSI sets the standard for quality in medical laboratory testing. A not-for-profit membership organization, CLSI brings together the global laboratory community for the advancement of a common cause: to foster excellence in laboratory medicine.  

For nearly 50 years, our members, volunteers, and customers have made CLSI a respected, transformative leader in the development and implementation of medical laboratory testing standards. Through our unified efforts, we will continue to set and uphold the standards that drive quality test results, enhance patient care delivery, and improve health care around the world.

By using CLSI standards, laboratorians can improve process quality, speed the development of standard operating procedures, and implement safer practices with greater ease and efficiency.



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