Abstract： ObjectiveTo establish a radioligand assay for protein tyrosine phosphatase autoantibody (IA-2A).Methods 35 S labeling recombinant human IA-2 antigen wa s obtained by in vitro transcription and translation, and then mixed with serum samples in self-made rotating incubator overnight. The IA-2 immunocomplex was precipitated with protein A-agarose, then washed with TBST buffer and counted i n CPM using liquid scintillation counter The results were expressed by IA-2A index. The sensitivity and specificity of the assay were evaluated in the 3rd Di abetes Autoantibody Standardization Program (DASP) 2003 sponsored by the Immuno logy of Diabetes Society (IDS). Also, IA-2A was screened in Chinese diabetic patients (type 1, n=111; type 2, n=113) and healthy controls(n=125 ).ResultsThe intra-assay coefficient of variation (CV ) was 3.2%～9.7%, inter-assay CV 5.6%～11.7%. The IA-2A indices of 45 sa mp les were tested in our laboratory and an international standardized laboratory, which were totally consistent. The IA-2A index cut point was determined accord ing to the upper limit of 99.5 percentile of 125 healthy controls. The index of 0.0065 or higher was defined as positive. The IA-2A positive prevalence was 23 .4 (26/111) in type 1 diabetes and 1.8 (2/113) in type 2 diabetes (χ 2=24.0 ,P<0.001). The IA-2A positive percentage in type 1 diabetic patients was higher in the course of less than 1 year than over 1 year (33.3% vs 15.0%, P <0.05).ConclusionThe established IA-2A radioligand assay h as a high sensitivity, specificity and reproductivity, and it could be used wid ely in clinical practice.