Controls and Result Interpretations in Studies of Urine Gluten Peptide Determinations

Monitoring coeliac disease in 2024, time to change practice?

PURPOSE OF REVIEW

Persistent villous atrophy is associated with morbidity in coeliac disease and most commonly due to ongoing gluten ingestion. Current methods for assessing gluten exposure and persisting villous atrophy include dietary questionnaires and repeat duodenal biopsy, which have limited accuracy or are invasive. This review discusses adjunctive and/or novel tests that could be used to overcome these challenges.

RECENT FINDINGS

Small bowel capsule endoscopy is well tolerated and helps to evaluate for persisting villous atrophy and importantly, complications associated with coeliac disease. Testing for urinary and/or stool gluten immunogenic peptides may help identify recent gluten exposure, but further studies are still warranted to evaluate the accuracy and applicability of this approach. Measuring spikes in circulating Interleukin-2 following gluten challenge has shown promise for coeliac disease diagnosis, and thus may serve as a useful confirmatory test in those with persisting symptoms but provides no information on mucosal inflammation. No specific gut microbial signature has been identified in coeliac disease; however, studies have shown a reduced microbial diversity in active disease, which with future refinement may prove clinically useful.

SUMMARY

There is no evidence to support alternative methods for assessing persisting villous atrophy in coeliac disease over performing an up-to-date duodenal biopsy. Monitoring for adherence to a gluten-free diet remains clinically challenging and should be a priority for future research.

Evaluation of a Single Determination of Gluten Immunogenic Peptides in Urine from Unaware Celiac Patients to Monitor Gluten-Free Diet Adherence

INTRODUCTION AND AIM

Usually, adherence to the gluten-free diet (GFD) in celiac patients is indirectly assessed through serological analysis, questionnaires, or invasive methods such as intestinal biopsy. The detection of gluten immunogenic peptides in urine (urinary gluten immunogenic peptides-uGIP) is a novel technique that directly evaluates the ingestion of gluten. The aim of this study was to evaluate the clinical efficacy of uGIP in the follow-up of celiac disease (CD).

METHODS

From April 2019 to February 2020, CD patients reporting complete adherence to the GFD were prospectively enrolled but were unaware of the reason for the tests. Urinary GIP, the celiac dietary adherence test (CDAT), symptomatic visual analog scales (VAS), and tissue transglutaminase antibodies (tTGA) titres were evaluated. Duodenal histology and capsule endoscopy (CE) were performed when indicated.

RESULTS

A total of 280 patients were enrolled. Thirty-two (11.4%) had a positive uGIP test (uGIP+). uGIP+ patients did not show significant differences in demographic parameters, CDAT, or VAS scores. The tTGA+ titre was not related to the positivity of uGIP (14.4% vs. 10.9% in patients with tTGA+ and tTGA-). Regarding histology, 66.7% of the GIP+ patients had atrophy compared to 32.7% of the GIP patients (p-value 0.01). However, the presence of atrophy did not correlate with tTGA. Mucosal atrophy was detected in 29 (47.5%) out of 61 patients by CE. With this method, no noticeable dependence on uGIP results (24 GIP- vs. 5 GIP+) was observed.

CONCLUSIONS

The single uGIP test was positive in 11% of CD cases referring a correct GFD adherence. Furthermore, uGIP results significantly correlated with the duodenal biopsy, formerly considered the gold standard for assessing CD activity.