Clinical significance and time course of antibodies to glutamic acid decarboxylase in Japanese children with type I (insulin-dependent) diabetes mellitus.

Although anti-glutamic acid decarboxylase antibodies (GADAb) have been reported to be a useful diagnostic and predictive marker of insulin-dependent diabetes mellitus (IDDM, type 1 DM) in Caucasians, a precise analysis of GADAb in Japanese children has not been reported. We examined the clinical significance and time course of GADAb in Japanese IDDM children, who have different genetic backgrounds from Caucasians. Twenty-three of 34 (67.6%) sera from recent-onset (< 6 months) IDDM, and 16 of 49 (32.7%) sera from long-standing (> or = 2 years) IDDM patients were positive for GADAb. This prevalence of GADAb in IDDM patients was significantly higher than in normal controls and the other groups including non-insulin-dependent DM, autoimmune thyroid disease and congenital hypothyroidism, and was also significantly higher in recent-onset than in long-standing IDDM. Time course analysis suggested that autoimmune response against GAD could follow different courses in individual cases after the initiation of insulin therapy. The incidence of GADAb was significantly higher in females than in males in the older age group (11-15 years). Other clinical features including residual pancreatic beta-cell function after diagnosis were demonstrated to be similar between GADAb-positive and -negative patients. In conclusion, this study using the newly established radioimmunoassay (RIA) for GADAb revealed a high prevalence of autoimmune reactivity to GAD in Japanese IDDM children. These results, using this RIA procedure, might assist in laying the groundwork for future trials of immunomodulation therapy for IDDM in Japan.