Clinical characteristics, GAD antibody (GADA) and change of C-peptide in Korean young age of onset diabetic patients

Aims To investigate the association of clinical and immunological markers with diabetes classification in newly diagnosed young diabetic patients at disease onset. Methods Eighty-two diabetic patients recruited within 1 year of onset (mean age 23.0 +/- 7.1, M:F = 46:36) were divided into three groups, namely: a low fasting C-peptide (FC) level at baseline group (the low FC group (n = 14, FC < 0.18 nmol/l)), an intermediate FC group (n = 29, 0.18 nmol/l less than or equal to FC < 0.37 nmol/l), and a high FC group (n = 39, 0.37 nmol/l less than or equal to FC). Patients were reclassified at follow-up (mean follow-up period 3.7 +/- 1.4 years) in the same manner as described above into low FC group (n = 31), intermediate FC group (n = 20), and high FC group (n = 31). The clinical characteristics and prevalence of GADA were compared. Results Patients in the high FC group at baseline had a higher body mass index (BMI), a higher frequency of a family history of diabetes, a higher meal-stimulated C-peptide increment, a lower frequency of ketonuria, a lower frequency of history of diabetic ketoacidosis, and a lower frequency of insulin therapy at diagnosis than those in the low and intermediate FC groups at baseline. Insulin secretory capacity, which was represented by fasting C-peptide, was affected by BMI at diagnosis and the presence of GADA. All the patients of the low FC group on follow-up were finally classified as having Type 1 diabetes; moreover, the factors that determined the type of diabetes were lower BMI at onset, GADA positivity, insulin therapy, lower fasting C-peptide level and lower meal-stimulated C-peptide increment at initial admission. Conclusions Our study suggests that follow-up involving C-peptide and GADA measurements in combination with clinical characteristics is useful for discriminating between the types of diabetes in these groups.