Antibodies to GAD in Japanese patients classified as Type 2 diabetes at diagnosis. High titre of GAD Ab is a predictive marker for early insulin treatment--report of west Japan (Kyushu, Yamaguchi, Osaka) study for GAD Ab(+) diabetes.

AIM: We evaluated the prevalence of GAD Ab in Japanese Type 2 diabetic patients treated with oral hypoglycaemic agents (OHA) and/or diet and followed GAD Ab(+) patients to assess the usefulness of GAD Ab as a marker for future insulin treatment prospectively. METHODS: A total of 2658 Japanese Type 2 diabetic patients treated by OHA and/or diet were randomly selected between April 1996 and December 1998. The clinical characteristics at entry were assessed and patients were followed for 1-3 years. RESULTS: The overall prevalence of GAD Ab among Type 2 diabetic patients was 2.0%. Forty-five had a history of diabetes of < or = 5 years (short history) while those with duration > 5 years (long history) totalled nine. Among them, 47% of patients with a short history did not require insulin in the follow-up period. However, none of those with a long history required insulin treatment within 2 years. Comparison of patients based on GAD titre in those with short history showed that 33% of patients in the high-titre group (> or = 20 U) required no insulin treatment in the first year of follow-up. In contrast, this proportion was 80% in the first and 67% in the second year in the low-titre group (< 20 U). CONCLUSIONS: The prevalence of GAD Ab in Japanese patients with a short and long history of diabetes was 2.8% and 0.9%, respectively. The presence of GAD Ab in Japanese Type 2 diabetic patients with a short history of diabetes is a marker for early insulin treatment.