Even for exempt media, labs must check for physical defects such as: Cracked Petri dishes or tubes. Excessive bubbles or rough surfaces. Obvious contamination or hemolysis. Incorrect agar depth (less than 3 mm) or unequal filling.
To move forward:
While commercial manufacturers perform the bulk of the testing, the clinical laboratory remains ultimately responsible for the quality of the media used in patient testing. Laboratories must: Verify that shipments arrive at the correct temperature. clsi m22a3 pdf
Document every type of culture media used in the lab and classify each as either "Exempt" or "Non-Exempt" according to M22-A3 tables.
Historically, clinical laboratories were required to perform extensive QC testing on every single batch of culture media received, regardless of its source. This process consumed vast amounts of time, reagents, and labor. CLSI M22-A3 introduced a risk-based approach, distinguishing between media with high failure rates and those with historically excellent performance records. Key Core Concepts of the Standard 1. Exempt vs. Non-Exempt Media Even for exempt media, labs must check for
Manufacture media under strict Good Manufacturing Practices (GMP).
One of the most significant contributions of the CLSI M22-A3 document is the classification of commercially prepared media into two main categories: and Non-Exempt . This classification is based on extensive multi-center studies evaluating the historical failure rates of various media types. 1. Exempt Media (Low Failure Rate) Incorrect agar depth (less than 3 mm) or unequal filling
While CLSI M22-A3 significantly reduces laboratory workload, implementation requires diligence:
Based on its content, features, and benefits, I would rate the CLSI M22A3 PDF document as follows:
Guidance on what to do when media fails QC: quarantining the lot, notifying the manufacturer, and deciding whether to use alternative media.
