High-Affinity ZnT8 Autoantibodies by Electrochemiluminescence Assay Improve the Risk Prediction for Type 1 Diabetes

Abstract

Background: A cohort of children with single ZnT8 autoantibody (ZnT8A) positivity were identified in two large clinical trials, Autoimmunity Screening for Kids (ASK) and Diabetes Autoimmunity Study in the Young (DAISY), and their risk of type 1 diabetes (T1D) have never been studied. Methods: Three cohorts were analyzed using a high-affinity electrochemiluminescence (ECL) ZnT8A assay including 302 new onset T1D patients, children with positive ZnT8A (n=135) by radio-binding assay (RBA) from 23400 general population children screened in the ASK study, and children (n=123) with multiple islet autoantibodies (IAbs) or single ZnT8A by RBA identified from 2547 longitudinally followed cases in DAISY. In addition, 1098 samples with all IAbs negative were also analyzed for ECL-ZnT8A. Findings: In ASK study, 0.58% (135/23400) of children were detected ZnT8A by RBA and 47.4% (64/135) of these ZnT8A were unexpectedly found as ZnT8A alone. Of 64 children with single ZnT8A, only 9 were detectable by ECL-ZnT8A. ZnT8A by RBA not confirmed by ECL were found low affinity with low risk. Positive predictive value of ECL-ZnT8A, in terms of high risk from T1D stage 1 to stage 3, was significantly higher (P<0.0001) than that of RBA-ZnT8A. Similarly in 2547 children of DAISY cohort, 11 cases in total were identified as single ZnT8A while only three who developed clinical T1D were detected ECL-ZnT8A. Interpretation: Majority of single ZnT8A positivity detected in screening by RBA were of low affinity with low T1D risk while ZnT8A detected by ECL assay were of high-affinity with high prediction for T1D development. Funding: JDRF, NIH Declaration of Interests: The authors declare no conflict of interest related to this study. Ethics Approval Statement: All subjects were provided written or electronic informed consent and all studies were approved by the University of Colorado Institutional Review Board.