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Randomized Controlled Trial
. 2021 Oct 6;12(10):e00411.
doi: 10.14309/ctg.0000000000000411.

Determination of Urinary Gluten Immunogenic Peptides to Assess Adherence to the Gluten-Free Diet: A Randomized, Double-Blind, Controlled Study

Chiara Monachesi  1 , Anil K Verma  1 , Giulia N Catassi  2 , Elisa Franceschini  2 , Simona Gatti  2 , Rosaria Gesuita  3 , Elena Lionetti  2 , Carlo Catassi  2   4
Affiliations
Randomized Controlled Trial

Determination of Urinary Gluten Immunogenic Peptides to Assess Adherence to the Gluten-Free Diet: A Randomized, Double-Blind, Controlled Study

Chiara Monachesi et al. Clin Transl Gastroenterol. .

Abstract

Introduction: The adherence to a gluten-free diet (GFD) is a trending topic in the management of celiac disease. The aim of our study was to evaluate the diagnostic performance of urinary gluten immunogenic peptides (GIP) determination to detect gluten contamination of the GFD.

Methods: In study A, 25 healthy adults on a standard GFD performed 6 gluten challenges (0, 10, 50, 100, 500, and 1,000 mg) with quantification of urinary GIP before (T0) and during the following 24 hours. In study B, 12 participants on a gluten contamination elimination diet underwent urinary GIP determination at T0 and after challenge with 5 or 10 mg gluten. Urine GIP concentration was determined by an immunochromatographic assay.

Results: In study A, 51 of 150 baseline urine samples were GIP+ on GFD and 7 of 17 were GIP+ after the zero-gluten challenge, whereas only 55 of 81 were GIP+ after the 10-1,000 mg gluten challenges. There was no significant change in the 24-hour urinary GIP when increasing gluten from 10 to 1,000 mg. In study B, 24 of 24 baseline urine samples were GIP-, whereas 8 of 24 were GIP+ after 5 or 10 mg of gluten.

Discussion: Traces of gluten in the standard GFD may cause positivity of urinary GIP determination, whereas a false negativity is common after a gluten intake of 10-1,000 mg. Owing to the impossibility of standardizing the test in normal conditions, it seems unlikely that urinary GIP determination may represent a reliable tool to assess the compliance to the GFD of patients with celiac disease or other gluten-related disorders.

Trial registration: ClinicalTrials.gov NCT04477239.

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Conflict of interest statement

Guarantor of the article: Carlo Catassi, MD, MPH, is the guarantor of the article and fully responsible for the conduct of the study.

Specific author contributions: C. M., A.K.V.: investigation, data curation, writing-original draft, writing-review and editing; G.N.C.: investigation, writing-review and editing; E.F., S.G.: conceptualization and methodology, writing-review and editing; R.G.: software and formal analysis; E. L., C.C.: conceptualization and methodology; writing-review and editing; C.C.: visualization and supervision; project administration. All authors read and approved the final version of the manuscript.

Financial support: None to report.

Potential competing interests: C.C. is a scientific consultant to Dr. Schär Food, Takeda, and NOOS Italy. The other authors declare no conflicts of interest.

Ethical clearance: The study was conducted in accordance with the principles of the Helsinki Declaration as revised in Fortaleza 2013 and was approved by the Ethical Committee of the Polytechnic University of Marche, Ancona, Italy (ID # 131530). The trial was registered in the clinicaltrials.gov registry (ClinicalTrials.gov ID # NCT04477239).

Figures

Figure 1.
Figure 1.
Flow chart of study A. GFD, gluten-free diet; T0, baseline.
Figure 2.
Figure 2.
Baseline (T0) urinary gluten immunogenic peptides determinations after 3 days of standard gluten-free diet. GIP, gluten immunogenic peptides; LD, limit of detection; LQ, limit of quantification.
Figure 3.
Figure 3.
Results of the 24-hour urinary GIP determination after the different gluten challenges in subjects performing the standard gluten-free diet. Crossed gray cells: samples excluded because of a positive T0 result. White cells: GIP-negative samples. GIP, gluten immunogenic peptides.
Figure 4.
Figure 4.
Comparison between the zero-gluten challenge and the gluten challenge urinary GIPs responses at different levels of gluten intake. P values refer to the Wilcoxon signed-rank test. GIP, gluten immunogenic peptides.
Figure 5.
Figure 5.
Observed (dotted line) and estimated ROC curves (solid line) with 90% confidence bands (gray area). AUC, area under curve; CI, confidence interval; ROC, receiver operating characteristics.
Figure 6.
Figure 6.
Results of 24-hour urinary GIP determination before and after the 5 mg (a) and the 10 mg (b) gluten challenge in subjects performing the gluten contamination elimination diet. White cells: GIP-negative samples. GIP, gluten immunogenic peptides.
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References

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