The GLU-10: a validated ten-point score to identify poorly instructed celiac patients in need of dietary interventions.

Background: A standard tool to assess patients' knowledge about gluten and the gluten-free diet (GFD) is lacking.

Methods: We aimed to develop and validate a questionnaire to assess GFD knowledge. A 10-point questionnaire (GLU10) covering different aspects of knowledge about gluten content in food/non-food products and the gluten-free living was developed. To validate this questionnaire, it was administered to adult celiac patients already instructed on gluten and the GFD and non-celiac controls. Patients were prospectively recruited at our Gastroenterology Outpatient Clinic between August 2020 and February 2021.

Results: One hundred and six patients (52 celiac patients and 54 controls) participated in the validation phase. Celiac patients scored significantly higher than controls on the GLU10 Questionnaire (median 6 points vs. 2 points, P<0.001). Higher self-reported knowledge of the GFD was related to a higher score (P<0.001). ROC curve confirmed the ability of the GLU10 Questionnaire to discriminate between subjects with good and poor GFD knowledge (AUC=0.94, 95% CI: 0.90-0.98). A score of 5 was identified as the best cut-off (sensitivity 80.8%, specificity 94.4%). On multivariable logistic regression analysis, being a celiac patient (P<0.001) and having a university degree (P=0.04) were associated to a high GLU10 Score (≥5).

Conclusions: GLU10 is the first validated questionnaire for assessing knowledge of a GFD in celiac patients and the general population.