Verification of Antimicrobial Susceptibility Testing Methods: a Practical Approach

The process of verifying an antimicrobial susceptibility testing (AST) system can be very confusing. There are different AST methods, such as MIC methods and disk diffusion testing. In addition, there are several different reasons why verification might be necessary, such as implementing a new method in the laboratory or implementing non-FDA interpretive criteria or breakpoints on an FDA-cleared AST system. The Clinical Laboratory Improvement Amendment (CLIA) provides some general guidance, but ultimately, it is the responsibility of a laboratory director to decide the composition of a verification study protocol. Variables to consider are what methods should be compared, what and how many isolates should be tested, how the results will be compared, and what study results will result in an acceptable study outcome. This article provides some general guidelines for developing and conducting a verification study of an AST system.