The Possible Role of Anti-Glutamic Acid Decarboxylase Antibody Levels in the Development of Celiac Disease in Children with Type 1 Diabetes

Objective This study evaluated whether metabolic status and diabetes-related autoantibody levels at the time of type 1 diabetes diagnosis are associated with subsequent celiac disease in children. Methods This retrospective matched case–control study included children diagnosed with type 1 diabetes between 2015 and 2025. Twenty-two children who developed celiac disease during follow-up were compared with 44 age- and sex-matched children with type 1 diabetes who did not develop celiac disease. Celiac disease was diagnosed based on serology and duodenal histopathology. Baseline acid-base status, C-peptide, glycated hemoglobin, and diabetes-related autoantibodies were analyzed. Results Among 238 children with newly diagnosed type 1 diabetes, 22 children (9.2%) developed celiac disease. These children were compared with 44 age- and sex-matched children with type 1 diabetes who did not develop celiac disease. The median interval from diabetes diagnosis to celiac disease diagnosis was 8.5 months. Celiac disease was diagnosed within the first year in 59.2%, within the first 2 years in 86.3%, and within the first 3 years in 95.4% of affected children. Baseline acid-base status and C-peptide levels did not differ between groups. Anti-glutamic acid decarboxylase levels were higher in children who later developed celiac disease. Using a cut-off value of 66.5 IU/mL, anti-glutamic acid decarboxylase positivity was associated with increased odds of celiac disease development. This association remained significant in exploratory multivariable analysis after adjustment for anti-insulin antibody, islet cell antibody, and C-peptide levels. Conclusions Baseline acid–base status and C-peptide levels were not associated with subsequent celiac disease in children with type 1 diabetes. Anti-glutamic acid decarboxylase≥66.5 IU/mL remained independently associated with subsequent celiac disease after exploratory adjustment for other diabetes-related autoimmune markers and C-peptide levels. Given the limited sample size and retrospective design, this finding should be considered hypothesis-generating and requires validation in larger prospective cohorts. Regular serological screening for celiac disease after the diagnosis of type 1 diabetes remains essential, regardless of baseline autoantibody status.