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

PAGE FIVE – SELECTIVITY STUDY - CROSSREACTIVITY

Cross-reactivity The matrices identified in Annex A, Table 2, at full, undiluted

concentration (with some exceptions as noted), will be prepared and analyzed with the candidate method as it is designed for testing food products. One test portion of each blank food material should be analyzed according to the entire method protocol. In the event that an unclaimed matrix tests above the method LOQ or lowest non-zero standard, it or another example of the same matrix may be retested in six test portions, to rule out cross-reactivity. If the result persists, the extract must be diluted and rerun to characterize the extent of the cross-reactivity, and the test material may also be evaluated with an alternative method (PCR, Western blot, mass spectrometry, alternate ELISA, etc.) to verify whether the signal is the result of cross-reactivity or a true positive due to cross-contact. Most of the commodities for Cross-Reactivity and Interference Studies of Annex A,Table 2 are flours. In case of a matrix (flour) tests above the method LOQ, the use of the same matrix in grain/bean format and ground in the method developer's lab to rule out contamination during the flour manufacturing process should be contemplated.