AOAC Guidance on FA Immunoassay Validation (August 2023)

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5.2.3.3. Interference

5.2.3.3.1. Study Design

5.2.3.3.1.1. One test portion should be spiked with the target analyte at a concentration that is three times the lowest LOQ claimed by the method to evaluate

interference.

5.2.3.3.1.2. Testing should be based on the full-strength extracts, i.e., a sample of the item being tested for cross-reactivity should be extracted using the extraction buffer and procedure outlined in the method instructions, then analyzed at 5.2.3.3.1.3. Certain concentrated food ingredients may require dilution (e.g., colors, spices, gums, etc.). Such ingredients may be tested at a 10% concentration in a matrix such as rice flour. If this type of dilution is conducted during method validation, corresponding procedures for specific food ingredients must be stipulated in the method protocol, kit insert, validation certificate, and full strength to determine if it leads to a positive result. (9)

validation report.

5.2.3.3.1.4. In general, food items tested for cross-reactivity should be prepared as they

would normally be analyzed (raw or cooked).

5.2.3.3.2. Data Analysis and Reporting

5.2.3.3.2.1. The calculated quantitative values for all spiked samples must be reported. 5.2.3.3.2.2. All results must be reported. If any analysis is repeated, both datasets must be

reported, and a justification given for all repeat analysis.

5.2.3.3.3. Acceptance Criteria

5.2.3.3.3.1. Spiked samples should render a result above the lowest LOQ.

5.2.3.3.3.2. The percent recovery should be calculated and reported for each tested food.