Research published in the European Journal of Gastroenterology and Hepatology shows that two enzyme-linked immunosorbent assay (ELISA) kits currently on the market for testing the gluten content in food are comparable and robust, accurately detecting 1.5 parts per million (ppm) of gliadin in apparently gluten-free food.
These findings emerge from a study, conducted by the Working Group on Prolamin Analysis and Toxicity, in which the investigators sought to validate two R5 monoclonal antibody-based ELISA kits, one supplied by R-Biopharm AG in Darmstadt, Germany, and the other by Ingenasa in Madrid, Spain.
Frederick Janssen, from Fascoda Food Consultancy in Coehoorsingel, The Netherlands, and associates explain that the kits were designed to sensitively assess the gluten status of a gluten-free diet, in order "to enable national food-law authorities to enforce legislation on dietary gluten-free products." As such, an analytical method is needed "which enables the measurement of gluten at low levels (typically from 10 to 200 ppm)."
They sent 12 samples of gluten-free cereal foods usually used as a replacement for gluten-containing cereals in a gluten-free diet to 20 laboratories. The samples comprised maize flour bread (n=4), rice dough (n=3), and contaminated gluten-free samples (n=5). All contained gliadin at levels ranging from 0-168 ppm.
The two kits appeared to be capable of determining gliadin contamination accurately from a concentration of 1.5 ppm, up to a concentration of 10 ppm.
The average recovery values ranged from 65% to 110%. The reproducibility figures ranged from 23 to 33 units for the R-Biopharm AG product, and from 23 to 47 units for the Ingenasa product.
Moreover, the repeatability figures ranged from 11 to 22 units, and from 13 to 25 units, for the R-Biopharm AG and the Ingenasa products, respectively.
Based on these results, the researchers conclude that both methods are therefore suitable for determining gliadin contamination up to around 10 ppm of gliadin.
"Both kit suppliers fulfill the criteria of the gliadin ring trial and it is shown that both ELISA kits guarantee the sensitivity of a new limit for gluten-free food," the authors state.
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