Suboptimal adherence to a gluten-free diet in adults with both type 1 diabetes and celiac disease using urinary gluten immunogenic peptide measurement.

Objectives: Concurrent type 1 diabetes (T1D) and celiac disease (CeD) pose challenges in insulin dosage adjustments and gluten-free dietary adherence. Urine testing for gluten immunogenic peptides (GIP) is a new method to detect gluten exposure within the last 3-12 h. Our aims were to compare gluten-free dietary adherence between T1D + CeD and CeD individuals and evaluate urinary GIP testing in an outpatient setting.

Materials and methods: This observational cross-sectional study included three adult groups: (1) T1D and CeD, (2) CeD only, and (3) T1D only. T1D participants were recruited from outpatient clinics, the CeD group via social media. One urine sample (12 pm-7 pm) was analyzed using a qualitative immunographic GIP test. CeD participants completed 'Celiac Dietary Adherence Test' (CDAT) and 'Celiac Symptom Index' (CSI) questionnaires. IgA anti-transglutaminase 2 (IgA-TG2) and IgG anti-deamidated gliadin (IgG-DGP) serology were also analyzed.

Results: 197 participants, mean (SD) age 43 (15) years, were included. Female percentages were: CeD: 90%, T1D + CeD: 64%, and T1D: 47%. Positive urinary GIP was found in 15% (14/96) of T1D + CeD and 0% (0/50) of CeD (p = 0.002). As expected, most T1D only participants had positive urinary GIP (86%, 44/51). CDAT and CSI scores did not differ between T1D + CeD and CeD groups. Positive IgA-TG2 and/or IgG-DGP levels were found in 12% of T1D + CeD and 6% of CeD participants (p = 0.38).

Conclusions: A single GIP urine test revealed higher gluten exposure in T1D + CeD versus CeD only, questioning dietary adherence in this population. Urinary GIP tests can be useful for clinical follow-up.