Enzyme-linked immunosorbent assay of 3 Screen Islet Cell Autoantibody in patients with autoimmune thyroid disease.

Background: In recent years, the emergence of multiplex technology that can simultaneously measure multiple anti-islet autoantibodies has become particularly valuable for the staging and early diagnosis of immune-mediated type 1 diabetes (T1D). While it has been established that 20%-30% of T1D patients suffer from autoimmune thyroid disease (AITD), there is limited available data regarding the presence of anti-islet autoantibodies in AITD patients. Among commercially available anti-islet autoantibodies, glutamic acid decarboxylase 65 autoantibodies (GADAs) are often the first marker measured in general clinical practice.

Aim: To investigate the frequency of anti-islet autoantibodies in AITD patients.

Methods: Our study involved four hundred ninety-five AITD patients, categorized into three distinct groups: AITD with T1D ( = 18), AITD with phenotypic type 2 diabetes (T2D) ( = 81), and AITD without diabetes ( = 396), and the enzyme-linked immunosorbent assay (ELISA) was employed to determine the frequencies of 3 Screen Islet Cell Autoantibody (3 Screen ICA), GADA, insulinoma-associated antigen-2 autoantibodies (IA-2As), and zinc transporter 8 autoantibodies (ZnT8As) within these groups.

Results: The frequency of 3 Screen ICA in AITD patients with T1D, T2D, and those without diabetes were 88.9%, 6.2%, and 5.1%, respectively, with no significant difference seen between the latter two groups. Notably, the frequency of 3 Screen ICA was 11.1% higher in AITD patients with T1D, 1.3% higher in AITD patients with T2D, and 1.1% higher in AITD patients without diabetes compared to GADA, respectively. Furthermore, 12.5%, 20.0%, and 20.0% of the 3 Screen ICA-positive patients were negative for GADA. Additionally, 1.3% of the AITD patients who tested negative for 3 Screen ICA in both the AITD with T2D and non-diabetic AITD groups were found to be positive for individual autoantibodies. Among the 3 Screen ICA-positive patients, there was a significantly higher proportion of individuals with multiple autoantibodies in AITD patients with T1D compared to those without diabetes (37.5% 5.0%, < 0.05). However, this proportion was similar to that in AITD patients with T2D (20.0%). Nevertheless, there was no significant difference in 3 Screen ICA titers between AITD patients with T1D and those without diabetes (436.8 ± 66.4 308.1 ± 66.4 index). Additionally, no significant difference in 3 Screen ICA titers was observed between Graves' disease and Hashimoto's thyroiditis in any of the groups.

Conclusion: Our findings reveal that some AITD patients without diabetes exhibit 3 Screen ICA titers comparable to those in AITD patients with T1D. Thus, 3 Screen ICA outperforms GADA in identifying latent anti-islet autoantibody-positive individuals among AITD patients.