AOAC GFA Stakeholder Program Meeting Book (August 27, 2023)

PAGE TEN – PRODUCT CONSISTENCY AND STABILITY

Product Stability and Consistency … A minimum of three separate product lots must be evaluated (…) If conducted separately from the matrix/intermediate precision studies, test materials used in the evaluation should be made in any one matrix claimed for the method, using all claimed gluten sources, or using stable control materials, as long as these go through the entire testing process from extraction to interpretation. Test materials should consist of a blank, as well as a test material spiked at three times the LOQ of the method (as long as that is equal to or below 20 mg/kg, otherwise test at 20 mg/kg). Five test portions should be analyzed for each test material in each of the three kit lots. Results should be analyzed to determine mean results, repeatability standard deviation, and recovery for each lot. For a product stability and consistency study conducted separately from the matrix study, data should be analyzed by ANOVA. If product stability and consistency are included in a nested design for the matrix study, data should be analyzed according to the ANOVA procedure outlined in Annex D. For the product stability and consistency study, there should be no significant (p< 0.05) differences between test kit lots and no significant effect of storage time. 4.7 Product Stability and Consistency 6 th paragraph “For the product stability and consistency study, there should be no significant (P<0.05) differences between test kit lots and effect of storage time.” Is there actually enough replication to determine significant time/age difference? It might also be possible that there is a significant difference between time/age of kits, but that older kits still meet all statistical requirements _and_ perhaps even perform closer to true on recoveries for certain sources.