Beginning in 1985, state-of-the-art surveys by the College of American Pathologists (CAP) led to M22-A guidelines by the National Committee for Clinical Laboratory Standards (NCCLS) for quality assurance (QA) of various commercially prepared isolation and diagnostic microbiology media. Some medium types were declared exempt from routine QA testing by each laboratory user, but manufacturer QA was maintained and specified in great detail. No update has occurred in more than 15 years as more complex media have been introduced into clinical microbiology practice.
To reassess the quality of commercially prepared microbiology media in the United States for the revision of NCCLS document M22-A2. Methods.-A questionnaire was designed to conform to that used by the CAP in 1985 and 1988, and was updated by lists of 52 recently introduced diagnostic media. Queries included details of laboratory QA in the last 12 months, such as number of lots tested, number of items in a lot, number of items in a quality control (QC) sample, number of lots failed, and reasons for lot failure. All CAP Microbiology Surveys participants received the document in late 2001.
Data from nearly 300 000 media lots representing 32.7 million medium items were received from more than 3000 CAP Surveys subscribers. Lot raw data failure rates for all media ranged from 0.10% to 9.87% (average, 1.01%). Failures with media having a significant QC experience (> or =1000 lots or > or =100 000 items) adjusted for QC strain-based failures (so-called extrapolated failure rate) ranged from 0.04% to 1.34% (average, 0.40%). The threshold rate for QA exemption from 1985 analyses was expanded to 0.50% or less and now allows exemption of 27 media evaluated in this study. Local laboratory QA must remain in force (M22-A2) for the other 25 products.
Generated QA failure results from the CAP Microbiology Surveys supplement recent results of the NCCLS M22 Subcommittee that will lead to more practical media QA guidelines and could significantly decrease costs for clinical microbiology laboratories through focusing QC on a smaller number of the most at-risk diagnostic products.