Performance of Celiac Serologic Markers and Follow-Up Adherence in Children with Type 1 Diabetes and Comorbid Celiac Disease

INTRODUCTION: Children with type 1 diabetes mellitus (T1D) have an increased risk of developing celiac disease (CeD), and those with comorbid conditions face increased healthcare demands. This study assessed celiac serology diagnostic performance and CeD follow-up rates in children with T1D and CeD. METHODS: Single-center retrospective review of children (≤18 years) diagnosed with T1D between 2000 and 2021. Controls included children with CeD without T1D, matched on age and gender at tissue transglutaminase (TTG) IgA positivity. Screening for CeD was done following T1D diagnosis. AUC-ROC was used to determine a TTG IgA cutoff for discriminating between those with confirmed CeD and those without CeD. Kaplan-Meier and Cox proportional hazard analyses were used to test whether children with T1D+CeD had different times to TTG IgA normalization than children with CeD-only. Negative-binomial regression was used to test whether children with T1D+CeD had different rates of follow-up with pediatric gastroenterology than children with CeD-only. RESULTS: Among 734 children with T1D, 591 (80.5%) underwent TTG IgA screening. A total of 70 (11.8%) had positive TTG IgA; of those, 43 (61.4%) had confirmed CeD. TTG IgA ≥3.62 times upper limit of normal (ULN) discriminated between biopsy-confirmed CeD and those without CeD (sensitivity 90%, specificity 92%, PPV 93%, NPV 89%). Among 37 children with T1D with positive TTG IgA and endomysial antibody (EMA), 25 had positive EMA (21 confirmed CeD), while 12 had negative EMA (none with CeD) (sensitivity 100%, specificity 75%, PPV 84%, NPV 100%). TTG IgA normalization took longer in T1D+CeD compared to CeD-only (median 6.5 versus 1.2 years, p < 0.001). Pediatric Gastroenterology CeD follow-up rates were lower in T1D+CeD subjects (0.33 versus 0.48 visits per person-year, p < 0.001). CONCLUSION: TTG IgA ≥3.6 times ULN or positive EMA is recommended to proceed with CeD confirmation. In cases of mild TTG IgA positivity, EMA can guide CeD confirmation given its high negative predictive value.