Interest of Urinary Measurement of Immunogenic Gluten Peptides (GIP) in the Follow-up of Pediatric Celiac Patients.

The effectiveness of care guided by urinary GIP testing, combined with reinforced dietary assessment by a dietitian, will be evaluated at Month 12 using urinary GIP measurements. A positive GIP result is defined as evidence of recent gluten ingestion. The test provides an immediate binary outcome (positive or negative).

At each assessment time point, patients will be classified as GIP-positive if at least one of the three urine tests performed is positive. At baseline (M0), where only a single test is conducted, GIP status will be determined based on that result alone.

Assessment of the correlation between urinary glucose-dependent insulinotropic peptide (GIP) results, measured using the iVYCHECK GIP Urine Test (reported as positive or negative), and the presence of gastrointestinal symptoms. Symptoms are defined as the presence of at least one of the following: abdominal pain, diarrhea, constipation, abdominal distension, or weight loss. Symptom presence will be recorded as a binary outcome (yes/no).

Assessment of the correlation between urinary glucose-dependent insulinotropic peptide (GIP) results, measured using the iVYCHECK GIP Urine Test (reported as positive or negative), and the assessment of gluten intake performed by a pediatrician.

Gluten intake will be evaluated using a standardized clinical assessment based on parental interview and dietary review, and recorded as a binary outcome (gluten intake: yes/no). This assessment includes: voluntary consumption of gluten-containing foods, verification of product labels for gluten content, and evaluation of food choices during meals outside the home.

Assessment of the correlation between urinary glucose-dependent insulinotropic peptide (GIP) results, measured using the iVYCHECK GIP Urine Test (reported as positive or negative), and anti-transglutaminase antibody levels measured in serum using an enzyme-linked immunosorbent assay (ELISA), expressed in international units per milliliter (IU/mL).

Serology results will be analyzed both as a continuous variable (IU/mL) and as a categorical variable defined as negative (< 7 IU/mL) or positive (≥ 7 IU/mL), according to standard laboratory thresholds.

Serological assessments will be performed according to routine clinical care at Month 0 (baseline), Month 6, and/or Month 12, as prescribed by the treating physician, in both the experimental and control groups.

Parental/child satisfaction will be assessed using a Likert scale responding to the following question: 'Does urinary GIP measurement during follow-up reassure you about proper adherence to the gluten-free diet?' This question will be asked to patients over 13 years old or to parents if the child is under 13 years old, with 5 possible response levels, from strongly agree to strongly disagree.