Antibodies to GAD in Japanese diabetic patients: a multicenter study.

We determined the prevalence of antibodies to glutamic acid decarboxylase (anti-GAD) in Japanese diabetic patients. Anti-GAD were detected by RIP Anti-GAD Hoechst, which is a new sensitive radioimmunoassay (RIA) kit using purified pig brain GAD as the antigen. One thousand nine hundred Japanese patients were collected by the Study Group for Antibodies to GAD. The prevalence of anti-GAD in the subjects of this study was: 35.4% (326/921) in all patients with IDDM, 50.3% (96/191) in patients with IDDM less than 1-year duration, 4.3% (29/680) in NIDDM, 37.9% (39/103) in slowly progressive IDDM, 10.5% (4/38) in gestational diabetes mellitus, 0% (0/27) in impaired glucose tolerance, 4.8% (6/124) in the school children with glycosuria, 2.1% (1/47) in the relatives of IDDM and 5.0% (1/20) in neurological diseases without diabetes. The prevalence in normal subjects was 2.2% (7/323). Anti-GAD are frequently detected by the RIA kit in patients with IDDM of short duration and this assay may be useful for population screening for IDDM and for better understanding of its pathogenesis.