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 ≤ 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 (≥ 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.