Gluten-related immunogenic peptides in stool as means to monitor compliance with gluten-free diet in children with newly dia gnosed coeliac disease

Abstract

Objectives and study: To compare the values of gluten-related immunogenic peptides (GIP) in stool and anti-tissue transglutaminase IgA antibodies (anti-tTG IgA) in blood in children newly diagnosed with coeliac disease (CD). Methods: All children (2–15 y) newly diagnosed with CD between May 2018 and May 2020 at our clinic who complied with the inclusion criteria were invited to join the prospective study. During workup for CD, a stool sample to measure GIP was taken together with a blood sample to measure anti-tTG IgA. All newly diagnosed children were invited 4 months later for a check-up. Children and their caregivers were asked about known non-compliance with the gluten-free diet (GFD), a blood sample was taken to measure the anti-tTG IgA, and a stool sample was collected to measure GIP. Blood was evaluated for anti-tTG IgA by ELISA, and the stool was tested by quantitative Sandwich ELISA designed to detect and quantify GIP using the G12 antibody. Values of GIP and anti-tTG IgA were compared in terms of their relation to the upper limit of normal (ULN) of the particular method. Results: 29 children (18 girls) were enrolled in the study. The values of GIP in stool at the time of diagnosis were above the ULN (0.15 µg/g) in all children. Average 4.21, median 3.29, standard deviation (SD) 3.7. After the four months, all but three (89.7%) had values of GIP in the reference range. Average 0.29, median 0.12, SD 0.73. Similarly, anti-tTG IgA values were above the ULN (9.9 U/mL) at the time of diagnosis in all children. Average 164, median 195, SD 49. Although the anti-tTG IgA levels were lower at check-up in all but one child, only 10 (34.5%) showed values within the normal range, with an average of 27.9, median 12.0, and SD 38.9. All children declared strict adherence to GFD. Discussion: Using the GIP concentration in stool, adherence to GFD in our cohort of children is very good, better than that described in literature. Conclusion: Measuring GIP in stool could prove a more sensitive indicator of adherence to GFD in the early months after the diagnosis of CD when anti-tTG IgA are still elevated above the ULN due to their well-described gradual decrease after GFD initiation.