Detection and quantification of gluten immunogenic peptides in feces of infants and their relationship with diet

Background: there are no effective methods to easily control the correct adherence to a gluten-free diet (GFD) in celiac disease (CD) patients. Aim: to assess the sensitivity and specificity of a rapid immunochromatographic (IC) test that detects gluten immunogenic peptides (GIP) in feces, compared to an enzyme-linked immunosorbent assay (ELISA) method. Methods: fecal samples from healthy infants were analyzed by a rapid IC test and ELISA, both methods are based on the anti-gliadin 33-mer monoclonal antibody. Group 1 included infants aged from 6 to 24 months, with an unrestricted consumption of gluten containing cereals. Group 2 (negative controls) was comprised of infants aged from 0 to 6 months, either breastfed or formula fed who had never ingested gluten. Results: in group 1 (n = 34), all infants had positive values by ELISA, the mean was 13.13 μgGIP/g (range 0.56-46.79). The IC test was negative in 5/20 cases and there was a significant correlation (p=0.006) between the mean daily gluten intake and GIP in feces. In group 2 (n = 20), all the samples were negative by both methods. Moreover, the Kappa Fleiss concordance index (Kappa = 0.79 CI95% [0.616, 0.965]) indicated a moderate concordance between both methods. Conclusions: according to our results, both methods are highly specific. However, the ELISA test had a higher sensitivity. Although we found a significant correlation between the amount of gluten consumed and GIP recovery in feces, further studies are needed to clarify the impact of individual confounding factors in GIP recovery.