Clinical and biochemical characteristics of nonobese type 2 diabetic patients with glutamic acid decarboxylase antibody in Korea

We evaluated the prevalence of glutamic acid decarboxylase autoantibody (GADA) in nonobese patients with type 2 diabetes mellitus in Korea and investigated the characteristics of GADA-positive and GADA-negative patients. Two years later, we assessed the progression of beta-cell function in these patients. Of the 647 nonobese patients with type 2 diabetes mellitus enrolled in the study, 10.1% was positive for GADA. Glutamic acid decarboxylase antibody–positive patients had lower fasting and stimulated C-peptide levels compared with GADA-negative patients (1.70 ± 0.72 vs 1.24 ± 0.59 μg/L, P < .001; 2.59 ± 1.51 vs 1.99 ± 0.82 μg/L, P < .001). Patients treated with insulin had lower fasting and stimulated C-peptide levels than those not treated (1.13 ± 0.52 vs 1.66 ± 0.73 μg/L, P = .002; 1.85 ± 0.69 vs 2.49 ± 0.91 μg/L, P = .004) and had higher titers of GADA (30.5 ± 7.3 vs 6.0 ± 4.8 U/mL, P < .001). In terms of progression of beta-cell function, fasting and stimulated C-peptide levels were significantly lower in GADA-positive patients after 2 years (from 1.24 ± 0.59 to 0.95 ± 0.54 μg/L, P = .004; from 1.99 ± 0.82 to 1.61 ± 0.77 μg/L, P = .007), whereas no such difference was observed in the GADA-negative patients. We demonstrate that a significant proportion of Korean patients may be positive for GADA; this is consistent with studies of white subjects, although disagrees with previous reports on Korean subjects. By assessing the presence of GADA in Korean type 2 diabetic patients, we are able to predict their course of beta-cell function and identify in advance those who are likely to require insulin treatment.