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.