Food Allergen Testing - Facts vs. Fiction (5)

Almost everyone working in the field of food allergen testing will have seen a single food sample produce remarkably different test results when it is analyzed with test kits from various manufacturers.

And the analyst would of course like to know which of the results is correct. Unfortunately, as allergen testing lacks reference methods and materials, it is difficult to claim that one kit is more accurate than another.

This fifth part of our series explains why results from different test kits are not always comparable.

The myth: All test kits on the market detect the same

It is highly improbable if not impossible that the performance of all commercially available test kits is the same. This is due to the lack of rules about which analyte an allergen test kit must detect. For each food allergen, there is a variety of different allergenic proteins with varying known conformations, but there is no recognized standard defining which of them must be detected. Therefore, we cannot assume that all test kits detect the same and consequently give comparable results.

Reasons for variability
Allergen test kits only have one thing in common: the overall analytical target (e.g. peanut). The rest of the kit could not pose more diversity. Commercially available test kits use different extraction buffers and procedures, which generate individual patterns of extracted allergenic proteins. Another crucial factor is the antibody used for the detection of the extracted proteins. Each antibody targets one specific epitope of the allergen, which is subject to modifications depending on the level of food processing. Different calibrators, individual cross-reactivities or matrix interferences, special reagents and the whole assay design are just a few more sources of inconsistent test kit results.

Coping with test kit diversity
Although not obvious at first sight, it may also be a benefit that most test kits on the market do not detect the same proteins. An antibody raised against the native allergen, will give accurate results when no extensive processing steps have been applied to the food preparation, but it will have difficulties if heat-treated products are to be analyzed or vice-versa. When choosing your test kit, a close discussion with the kit manufacturer is highly recommended as they can provide information about the test kit’s performance specifications.

Which is the best test kit for me?
In a food factory, analysts should carefully review and summarize all the processing steps that are applied to a food product to assess which kit is most suitable for their individual application. Service laboratories dealing with a wide variety of mostly unknown samples face challenges of kit diversity and comparability of test results. Often, a compromise between the performance with native and processed samples is most desirable. However, it is important to prove that results are consistent within each type of food.

 

This article was originally published in "International Food & Meat Topics", Volume 28 Number 5 (2017)

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