Objective Non-coeliac gluten sensitivity (NCGS) is characterised by intestinal and extraintestinal symptoms related to the ingestion of gluten-containing foods, in the absence of coeliac disease (CD) and wheat allergy. No biomarkers are available to diagnose NCGS and the gold standard double-blind placebo-controlled gluten challenge is clinically impractical. The aim of our work was to investigate the role of serum zonulin as a diagnostic biomarker of NCGS and to develop a diagnostic algorithm.
Design In a multicentre study, we enrolled 86 patients with either self-reported or double-blind confirmed NCGS, 59 patients with diarrhoea-predominant IBS (IBS-D), 15 patients with CD and 25 asymptomatic controls (AC). Zonulin serum levels were assessed and the associated diagnostic power calculated. Clinical and symptomatic data were recorded. The effect of diet on zonulin levels was evaluated in a subgroup of patients with NCGS.
Results Compared with ACs, the NCGS, irrespective of modality of diagnosis, and patients with CD had significantly increased levels of zonulin, as did both NCGS and patients with CD compared with participants with IBS-D. Self-reported NCGS showed increased zonulin levels compared with double-blind confirmed and not-confirmed NCGS. Six-month wheat avoidance significantly reduced zonulin levels only in HLA-DQ2/8-positive participants with NCGS. The diagnostic accuracy of zonulin levels in distinguishing NCGS from IBS-D was 81%. After exclusion of CD, a diagnostic algorithm combining zonulin levels, symptoms and gender improved the accuracy to 89%.
Conclusion Zonulin can be considered a diagnostic biomarker in NCGS and combined with demographic and clinical data differentiates NCGS from IBS-D with high accuracy. Wheat withdrawal was associated with a reduction in zonulin levels only in NCGS carrying HLA genotype.
- epithelial barrier
- functional bowel disorder
- irritable bowel syndrome
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Contributors GB, MRB, CC and AMM-L contributed to the study idea and design. MRB, CC, ADS, PG, GRC, MDS, GC, GL, CC, DF, LB, UV and GB contributed to data acquisition. MRB, CC, AMML, ADS, GRC, GL, CC, VS, UV and GB contributed to data interpretation. MRB, CC, AMM-L and GB wrote the first draft and all authors reviewed the manuscript for important intellectual content. AMM-L and MM contributed to the statistical analysis. MRB, ADS, PG, GRC, MDS, GC, GL, CC, DF, LB and UV provided technical or material support. GB supervised the study.
Funding The study was supported by the Italian Ministry of Education, University and Research, the University of Bologna and Fondazione del Monte di Bologna e Ravenna.
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval The protocol was first approved by the coordinating centre of Bologna (Independent Ethics Committee of St. Orsola-Malpighi Hospital; approval identification no: 91/2012/U/Tess), and then by all the other participating centres, and conducted in accordance with the Declaration of Helsinki and the principles of Good Clinical Practice. Each participant in the study gave written informed consent.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement All data relevant to the study are included in the article or uploaded as supplementary information.
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