Identifying Insulin Autoantibodies With Differential Risk in Type 1 Diabetes With a Novel Bridging ELISA

Insulin autoantibodies (IAAs) are commonly measured by radiobinding assays (RBAs), which detect both high- and low-affinity binding. Improved assays that preferentially detect high-affinity IAA are likely to provide greater specificity and thereby increase the diagnostic accuracy of IAA for early-stage type 1 diabetes (T1D). This study aimed to develop and validate a novel bridging ELISA for IAA detection. The bridging ELISA detects IAAs by their bivalent cross-linking of two proinsulin moieties in fluid phase. Validation was performed by using samples from 227 patients with newly diagnosed stage 3 T1D and 1,021 control participants. Additionally, 202 children positive for IAA by RBA from general population screening were tested by the bridging ELISA and electrochemiluminescence (ECL) assay. At 99.5% specificity, ELISA detected IAA in 65.2% of patients with stage 3 T1D vs. 60.8% by RBA. Among children identified as having RBA-positive IAA in general population screening, 80.3% of those with multiple islet autoantibodies and 48.1% of those with a single IAA had ELISA-IAA positive findings (P < 0.0001). For children with a single IAA by RBA, ELISA detected 78.9% of those with ECL-IAA-positive findings vs. 27.9% of those with ECL-IAA negative findings (P < 0.0001). Samples that were IAA negative by ELISA showed lower antibody affinity. The ELISA-IAA assay demonstrates high sensitivity and specificity and could become a practical tool for T1D population screening and clinical diagnosis across laboratories.

In global type 1 diabetes (T1D) population screening studies, there is an urgent need for a highly sensitive and specific insulin autoantibody (IAA) assay that can be implemented across multiple laboratories. This study aimed to develop and characterize a novel ELISA-based platform for IAA detection. We established a new bridging ELISA for IAA and validated it in cohorts of patients with stage 3 T1D, children positive for multiple and single islet antibodies, and control children negative for islet autoantibodies. The bridging ELISA-IAA assay demonstrates excellent sensitivity and specificity, preferentially identifies high-risk individuals, and offers a practical, scalable solution for T1D population screening and clinical diagnosis across laboratories.