Breakpoint Implementation Toolkit (BIT)
Effective January 2024, clinical laboratories performing antimicrobial susceptibility testing (AST) are required to use breakpoints currently recognized by Clinical and Laboratory Standards Institute (CLSI) or US Food and Drug Administration (FDA).
Together Clinical and Laboratory Standards Institute (CLSI), Association of Public Health Laboratories (APHL) , American Society for Microbiology (ASM), College of American Pathologists (CAP), and US Centers for Disease Control and Prevention (CDC), have jointly developed this Breakpoint Implementation Toolkit (BIT) to assist clinical laboratories in updating minimal inhibitory concentration (MIC) breakpoints.
Overview
The kit is designed to guide performance of a verification or validation study required to update breakpoints.
Also included are resources that explain the rationale behind breakpoint updates, regulatory requirements for updating breakpoints, and detailed instructions for performing an AST breakpoint validation or verification.
Manufacturers of AST systems can provide guidance on breakpoints used and clearance status with their systems.
Changes Since Original Publication
Date of Change
April 2025
Location of Change
Part B. CLSI vs. FDA Breakpointd
Comments
Replace 2023 Part B. CLSI vs. FDA Breakpoints
Contents
Introduction: Breakpoint Implementation Toolkit
Includes how to use the Breakpoint Implementation Toolkit, definitions, references, resources, and a Pathway for Updating Breakpoints (Figure 1).
Part A. Breakpoints in Use
Part A helps laboratories meet CAP requirements for documenting breakpoints in use in their laboratory.
Part B. CLSI vs FDA Breakpoints
Part B. includes a listing of all current CLSI breakpoints in M100-Ed34 with corresponding FDA breakpoints. This allows laboratories to identify whether their breakpoints, as identified in part A. of this toolkit, are current with CLSI and/or FDA breakpoints. Updated August 2024.
This spreadsheet contains a listing of ALL disk diffusion and MIC breakpoints (BPs) published in CLSI M100-34th edition. The FDA BPs are presented in the table if the CLSI BPs do not match the FDA BPs published on the FDA Susceptibility Test Interpretive Criteria (STIC) website as of June 11, 2024.
Part C. Breakpoint Implementation Summary
Part C is a template for documenting results of verification or validation studies to update breakpoints. This template can serve of evidence of support for your study for any accreditation or regulatory body.
Part D. CDC and FDA AR Bank BIT Isolate Sets
Part D includes CDC and FDA Antibiotic Resistance Isolate Bank isolate sets available for use in breakpoint verification and validation studies. It also specifies AR Bank Panels that are recommended for testing when using the BIT.
Part E. Instructions for Use of BIT Part F
Part E provides instructions for how to use part F, the prefilled Excel worksheet template. It contains MIC results from the AR Bank.
Part F. AR Bank Data Entry and Calculations
Excel workbook prefilled with the AR Bank BIT set isolates and their results. For earlier versions of MS Office/Excel that precede MS365, download the older version:
Part G. Blank Form for Data Entry
Part G is a template for validations or verifications using isolates other than those listed in the AR Bank BIT sets included in this toolkit.
Content Developed in Partnership With
