PANCREATIC BETA-CELL FUNCTION AND ANTIBODIES TO GLUTAMIC-ACID DECARBOXYLASE (ANTI-CAD) IN CHINESE PATIENTS WITH CLINICAL-DIAGNOSIS OF INSULIN-DEPENDENT DIABETES-MELLITUS

Antibodies to glutamic acid decarboxylase (anti-CAD) and pancreatic be ta cell secretory function were measured in 39 consecutive Chinese pat ients with a clinical diagnosis of insulin-dependent diabetes mellitus (IDDM) (19 males, mean +/- SD age, 37 +/- 15 years; body mass index ( BMI), 22 +/- 4 kg/m(2); mean duration of disease, 6.7 +/- 5.6 years). IDDM was defined on the basis of acute symptoms with heavy ketonuria ( > 3 +) or ketoacidosis at diagnosis, or requirement for continuous ins ulin treatment within one year of diagnosis. Insulin deficiency was de fined as a post-glucagon stimulated plasma C-peptide concentration les s than or equal to 0.6 nmol/l. Overall, anti-CAD antibodies were posit ive (> 18 units) in 23% (n = 9) of these patients. Of the 39 patients, 29 (74%) were insulin deficient and 10 (26%) were non-insulin deficie nt. Anti-CAD antibodies were positive in 31% of the insulin-deficient patients but in none of the non-insulin-deficient group. Insulin defic iency and anti-CAD positivity were associated with younger age, earlie r age of clinical onset and lower BMI. There were independent negative relationships between levels of anti-CAD antibodies and blood pressur e and a positive relationship between insulin dosage and albuminuria. This study emphasises the difficulty in differentiating clinically bet ween IDDM and NIDDM in Chinese patients. Despite the acute presentatio n, these patients had variable pancreatic beta cell secretory function . The varying duration of disease may partly explain the low prevalenc e of positive anti-GAD antibodies in these patients, but seems unlikel y to explain fully the difference from Caucasian IDDM patients.