Gliadin as a measure of gluten in foods containing wheat, rye, and barley-enzyme immunoassay method based on a specific monoclonal antibody to the potentially celiac toxic amino acid prolamin sequences: collaborative study.

The Working Group on Prolamin Analysis and Toxicity (WGPAT) organized a collaborative study to confirm whether the two R5 antibody-based ELISA test kits are able to detect gliadin in the lower mg/kg (ppm) level. Twenty laboratories investigated 12 blind-coded samples, spiked and naturally contaminated, to show the possibility of determining traces of gliadin in heat-treated or nonheat-treated foods by ELISA. It was shown that very small amounts of gliadin (below 100 ppm) could be detected by ELISA with a reproducibility RSD(R) (37%) and a repeatability RSD, (27%) common for ELISA under these conditions. The recovery of gliadin from the spiked samples was between 84 and 109%, based on the results of all laboratories, including those with poor performance. No false positives were found by the method (P < or =0.05), but one negative sample was contaminated during the bakery process. It is recommended that the method be accepted by AOAC as Official First Action.