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Before the widespread adoption of this standard, clinical laboratories were burdened with testing every single batch of culture media arriving at their facilities, regardless of whether it was purchased from a reputable manufacturer or prepared in-house. CLSI M22-A3 established a scientifically backed framework that differentiates between high-failure-rate media and highly stable media, fundamentally changing how laboratories allocate their QC resources. Core Objectives of the Standard The primary goals of the CLSI M22-A3 document include:
Yes. The standard requires lot-level testing per manufacturer. Different manufacturers may use different formulations or production processes, so performance can vary.
Chocolate Agar (except when used for fastidious organisms like Neisseria or Haemophilus ) Eosin Methylene Blue (EMB) Agar 2. Non-Exempt Media (Requiring Full User QC)
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Ensures that fastidious or critical pathogens are not missed due to substandard or degraded culture media.
All QC results must be logged. If a medium batch fails any parameter, the entire lot must be rejected, and the failure must be reported to the manufacturer. Evolution and the Transition to M22-A4
Commercial Control Materials for Susceptibility Testing; Approved Standard—Third Edition Publisher: Clinical and Laboratory Standards Institute (CLSI) Status: Withdrawn (Superseded by CLSI M22, M23, and M100 integration) This public link is valid for 7 days
The full title of this document is: "Liquid Chromatography in the Clinical Laboratory; Approved Guideline—Third Edition."
Even when utilizing exempt media, the laboratory cannot completely bypass quality checks. Under CLSI M22-A3, the user must:
: Guidelines for preparing inoculum (such as matching a 0.5 McFarland standard) and isolation streaking methods for quality verification. Key Specifications
Demonstrating that selective media successfully inhibits non-target organisms (e.g., testing MacConkey Agar with Staphylococcus aureus to ensure Gram-positive organisms are inhibited). Regulatory Compliance: CLIA, CAP, and Joint Commission Can’t copy the link right now
Laboratories must perform complete in-house QC testing on every new lot number or shipment received, regardless of manufacturer certification.
In the highly regulated world of clinical diagnostics and pharmaceutical analysis, precision is not just a goal—it is a legal and ethical requirement. For laboratories performing chromatographic assays, particularly those dealing with therapeutic drug monitoring (TDM), toxicology, and clinical chemistry, the document known as serves as the definitive roadmap.
If an exempt medium shows visual signs of deterioration (such as drying or discoloration), it must be discarded, and the failure should be reported to the manufacturer.
Ensuring non-target organisms are completely or partially inhibited.
The document outlines the responsibilities for both manufacturers and users to ensure media performance.