DIFFERING FREQUENCY OF AUTOANTIBODIES TO GLUTAMIC-ACID DECARBOXYLASE AMONG KOREANS, THAIS, AND AUSTRALIANS WITH DIABETES-MELLITUS

The wide racial-geographic differences in the incidence and prevalence of insulin-dependent diabetes mellitus (IDDM) between Europids and As ian populations prompted us to compare frequencies of positivity of au toantibody to glutamic acid decarboxylase (GAD). The patients with IDD M included 41 Koreans, 30 Thais, and 45 Australian Europids; the Korea ns included 14 cases regarded as atypical IDDM by reason of a delayed requirement for insulin treatment. Autoantibodies were measured by rad ioimmunoprecipitation using iodinated purified porcine brain GAD. The frequency of positive tests for anti-GAD of 30% (8/27) for Koreans and 51% (20/39) for Thais was significantly lower than the 84% (38/45) fo r Australian Europids, even after stratifying by age of onset. Corresp ondingly, the mean levels of anti-GAD among seropositive cases were si gnificantly lower for Koreans than for Australian Europids. In contras t to Thais and Australians, more than half the Koreans were diagnosed at age >20 years, but there was no significant difference in positivit y for anti-GAD between those over or under the age of 20 at diagnosis. The different frequency of positivity in tests for anti-GAD among Kor eans, Thais, and Australian Europids with IDDM suggests that there is a greater etiologic heterogeneity of IDDM among Asian than Europid pop ulations, in whom autoimmune destruction of pancreatic islets predomin ates. (C) 1995 Academic Press, Inc.