Immunoassays are based on the detection of proteins, more precisely on the specific interaction and binding of antibodies to antigens of animal origin present in the feed. Selected antibodies should be heat resistant as PAPs are heat treated in their production; furthermore they should reveal differences in molecular structure according to the taxonomic groups of interest (ruminant, porcine, etc). Several kits are available on the market for the purpose.

Two main applications are to be found:

• Enzyme linked immunosorbant assay (ELISA) for laboratory use
• Dipstick or lateral flow for field use

The use of immunoassays is limited to screening purposes and shall never been confirmatory for the presence of PAPs in feed. The EURL-AP team realised evaluations of several commercialized test kits. These studies revealed some inconsistencies of sensitivity (e.g lack of detection of ruminant PAPs in fish meals) but also of specificity (e.g false detection of PAPs in presence of beet pulp). It seems that those tests, not developed inside the European Union, are incompatible with the requirement of severe heat treatments for PAPs production.

Advantages

• Easiness and rapidity of test
• Possibility of automatic readers for results
• Field or industry use (quality control)

Disadvantages

• Limit of detection not low enough
• Screening method, no confirmatory test
• False positive and false negative results
• No quantitative