Other challenges revolve around how microorganisms that are intended for test panels are handled and stored. Significant variations exist among manufacturers. Those variations can influence microbe handling and storage, giving rise to possible differences in microorganism properties and characteristics.
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Inconsistency also exists with regard to shipping and traceability of the test panel microbes. Further, microorganisms contained in test panels generally are not tested and characterized, eliminating assurances of the cultures’ identity and purity. Because cultures are retained for use in test panels manufactured over multiple years, excessive sub-culturing of microorganisms is possible. This can also contribute to variation and inconsistency in the genotypic and phenotypic characteristics of the microorganisms in the test panels, which confounds efforts to compare test results from year to year.
Incorrectly identified, contaminated, or inconsistent proficiency test materials can affect on test evaluation. Laboratories undertaking proficiency tests are often judged to pass or fail based on their conformity to the majority of responding laboratories rather than on the accuracy of their results.
Aside from reducing the public health risks posed by the proficiency test samples, perhaps the paramount issue facing the clinical laboratory proficiency testing system is improving the validity of the assessment. Stable, well-characterized reference materials are prerequisites for valid quality assessment in clinical labs. Authenticated standard reference microorganisms bring consistency to the tests and allow results to be meaningfully compared among a group of laboratories. These features are absent if such reference material is not available for the panels and clinical isolates are used instead.
Proficiency test standards will address these challenges and improve lab safety, reduce public health risk, and increase the consistency of the materials. A standards program for proficiency testing will also help increase validity in microbiology proficiency testing programs by ensuring the use of authenticated organisms in test panels.
Implementing such a program would reduce liability for proficiency testing manufacturers, providers and laboratory directors and increase safety for lab workers. The microbiology proficiency testing system benefits by taking advantage of the expertise in handling, storing, authenticating, and distributing microorganisms offered by a biological resource center like ATCC. Specifically, the a proficiency testing standards program aims to improve the current situation in a number of ways:
- By providing dedicated proficiency testing stocks that are lot- and vial-traceable, accompanied by a detailed certificate of analysis, the chain-of-custody for the microorganisms in proficiency testing panels is established and documented;
- To improve year-to-year consistency, manufacturers will receive fresh strains each year and destroy remaining material when panel assembly is complete;
- Proficiency test standard microorganisms will be provided in vials labeled with serial numbers to allow traceability to the level of individual vials;
- Proficiency test standards intended for PT manufacturers will be lot-specific and will be assigned unique catalog numbers.
Joe Perrone is vice president of standards and certification, American type, for ATCC (Manassas, Va.). Reach him by contacting Scott Jenkins, ATCC’s director of communications, at 703-365-2879.