[Current status of methods and proficiency in assays for islet autoantibodies]

Objective: To investigate the current application status of detection methods and reagents for islet autoantibodies in domestic medical institutions, and to assess their detection proficiency. Methods: From October 15, 2024 to March 15, 2025, a total of 175 questionnaires were distributed to core network member units of the National Clinical Research Center for Endocrine and Metabolic Diseases, member units of the Chinese Diabetes Society and the Chinese Society of Endocrinology, member units of the China Type 1 Diabetes Alliance, and other relevant institutions. After collection, statistical analysis of detection methods for islet autoantibodies and the proportion of domestic reagents. Ten representative institutions were selected, and each was provided with 150 blinded and coded standardized evaluation samples (including 50 new-onset type 1 diabetes samples and 100 healthy donor samples). After each institution completes testing and submits the results, the national center uniformly analyzes the sensitivity, specificity and accuracy, as well as the consistency between test results from participating laboratories and those of the"gold standard"[radioligand assay (RLA) or electrochemiluminescence (ECL)]. Spearman correlation analysis was adopted to assess the correlation between the test results of participating laboratories and the gold standard measurements. Results: A total of 127 valid questionnaires were collected from all 31 provinces, municipalities, and autonomous regions in China. The proportion of institutions adopting chemiluminescence immunoassay(CLIA) was 76.6%(95/124), and that of domestic reagents used was 91.7%(121/132). Results from 10 institutions showed the following results: the median sensitivity values for glutamic acid decarboxylase autoantibody (GADA), protein tyrosine phosphatase-2 autoantibodies (IA-2A), insulin autoantibody (IAA), zinc transporter 8 autoantibody (ZnT8A) were 76.0%(range:38.0%-90.0%), 36.0%(range:8.0%-66.0%),24.0%(range:2.0%-50.0%), and 46.0%(range:0-54.0%), respectively; the median specificity values were 100.0%(range:98.0%-100.0%),100.0%(range:99.0%-100.0%), 98.0%(range:95.0%-100.0%),99.0%(range:98.0%-100.0%), respectively; the median accuracy values were 92.0%(range:78.0-96.7%), 78.7%(range:69.3-88.7%), 72.7%(range:66.0-83.3%), and 80.7%(range:66.0%-84.7%), respectively. The median concordance rates between test results from institutions and the "gold standard" were 95.7% (range:82.7%-100.0%) for GADA, 88.3% (range:80.7%-96.7%) for IA-2A, 87.3% (range:82.7%-92.0%) for IAA, and 94.4% (range:81.3%-96.0%) for ZnT8A. The median correlation coefficients (ρ) were 0.857 (range:0.780-0.905) for GADA, 0.829 (range:0.507-0.871) for IA-2A, 0.781 (range:0.601-0.811) for IAA, and 0.805 (range:0.448-0.887) for ZnT8A. Conclusions: At the present stage in China, the mainstream detection method for islet autoantibodies is CLIA, and reagents have basically achieved localization. Overall, the detection quality for GADA is relatively satisfactory; however, the detection levels of IA-2A, InT8A, and particularyl IAA, still need further improvement.