2377-P: Patterns of Type 1 Diabetes (T1D) Islet Autoantibody Testing in Adults with Autoimmune Thyroid or Celiac Disease

Introduction and Objective: Individuals with celiac disease (CD), Graves disease (GD) or Hashimoto thyroiditis (HT) are at increased risk of developing T1D, yet current screening guidelines focus on family history or genetic risk, potentially losing opportunity for prevention. Our objective was to examine national patterns of islet autoantibody testing in these high-risk populations. Methods: We conducted a cross-sectional study using national Epic Cosmos data, representing 300 M U.S. residents. We included adults aged ≥18 yrs with ≥1 abnormal celiac or thyroid autoantibody test between Jan 1, 2020, and Dec 1, 2025, and evaluated T1D islet autoantibody (IAb) testing frequency and positivity rates. Results: Among 636,622 adults with celiac or autoimmune thyroid disease (mean age 49±18 yrs, 78%F, 18% CD, 28% GD, 59% HT), only 13,880 (2.2%) ever underwent IAb testing. Among those IAb-tested, 35% screened positive (41% of CD, 34% of HT, 34% of GD). Conclusion: T1D islet autoantibody testing is low nationally among adults with preexisting celiac or autoimmune thyroid disease. Meanwhile, one-third of those IAb tested screened positive, highlighting missed opportunity of islet autoimmunity identification and potential prevention in these high-risk populations. Disclosure L. Rasquin Leon: None. S. Agarwal: None. J. Milosavljevic: None.