Urinary Gluten Peptide Determination: Results Are Results, Even When They Contradict Aprioristic Expectations

All laboratory procedures were performed in our specialized Celiac Disease Research Laboratory by 2 of us (C.M. and A.K.V.). Since we took several precautions to avoid confounding factors in a real-life scenario, as described in the Methods section, we do not see any reason to consider our results “inconsistent” simply because urinary GIP was often unexpectedly positive (in subjects on the gluten-free diet [GFD] or after the placebo challenge) or negative (after the gluten challenge). The high rate of false negative urinary GIP in subjects challenged with gluten (32%), likely related to interindividual variations in the metabolism of gluten peptides, is even more worrisome because it may generate an unjustified feeling of adherence to the GFD in celiac patients actually ingesting significant amounts of gluten. According to Karl Popper's principles of scientific research, our study awaits confirmation or confutation by other experimental investigations, possibly conducted by independent researchers with no direct interest in the commercialization of items/devices that are the object of the study.