Measurement of Gluten in Food Products: Proficiency‐Testing Rounds as a Measure of Precision and Applicability

In 2008, Codex Alimentarius endorsed the R5 Enzyme‐Linked Immunosorbent Assay (ELISA) method as Method Type 1 for gluten measurement in gluten‐free foods. The most recognized R5 ELISA test kit is the RIDASCREEEN® Gliadin (R7001; manufacturer R‐Biopharm). Beside collaborative tests that led to several international approved methods of this test kit, proficiency‐testing (PT) rounds are regularly performed in Europe by different PT providers. Results from these rounds were analyzed regarding the number of participating labs with acceptable results for the RIDASCREEN® Gliadin. All PT rounds document the excellent consistency and comparability of results. The data show that the RIDASCREEN® Gliadin R5 ELISA is also applicable to cake mix, oat‐based foodstuff, infant soya formula, cookies, canned boiled sausage, gravy thickener, pasta, and potato dumpling. These rounds also included the analysis of blank matrices. It was found that more than 95% of all participating laboratories correctly detected these samples as negative. Other gluten test kit manufacturers were analyzed as well, but due to the low number of participants using these test kits results were often only analyzed in a qualitative manner questioning the comparability of these kits to the RIDASCREEN® Gliadin R5 ELISA