In a randomized, placebo-controlled study, detection of stool gluten immunogenic peptide (GIP) surpassed symptoms, dietary adherence scores, urinary analysis, and coeliac serology in identifying intermittent gluten exposure in coeliac disease. This research by Amy K Russell et al. evaluated stool GIP excretion following a controlled low-dose gluten challenge aimed at simulating accidental gluten ingestion. Overall, 52 people affected with coeliac disease participated in this double-blind study involving either gluten (50-1000 mg) or placebo challenges.

Various parameters encompassing stool and urine GIP levels, symptoms, serological markers, and dietary adherence were examined. Stool GIP displayed 100% sensitivity in detecting gluten intake of ≥250 mg and 71% sensitivity for 50 mg. Peak GIP detection occurred between 12 to 36 hours post-gluten exposure, with stool GIP levels remaining quantifiable for up to 5 days following ingestion of 1000 mg of gluten. Examination of urine GIP revealed lower sensitivity in comparison with stool testing. During the lead-in period, the symptoms, dietary adherence scores, and serological markers did not show a correlation with the excretion of gluten.

Hence, stool GIP detection is highly sensitive and correlates with gluten dosage and time elapsed since ingestion. Implementing weekly or bi-weekly testing is proposed to ameliorate the detection of low-level gluten exposure compared to urine GIP assessments or conventional methods. Although a substantial proportion of patients showed baseline-positive GIP levels despite being seronegative and seemingly well-treated, further assessment of patient behavior and assay specificity is warranted.