Ethnic differences in C-peptide levels and anti-GAD antibodies in South African patients with diabetic ketoacidosis.
To determine differences between Black and White South Africans with diabetic ketoacidosis (DKA) and between Black patients on insulin vs. those on oral agents presenting with DKA, post stabilization fasting C-peptide levels and anti-glutamic acid decarboxylase (GAD) antibodies were measured together with serum glucose, acid base and urine ketones on admission. Of 60 patients with diabetic ketoacidosis (DKA) (76 admissions), the 43 Black patients had a higher BMI (23.1 vs. 20.0 kg/m(2), p=0.05) than did the 17 White patients, were more often newly diagnosed (37% vs. 1%, p=0.03), and a greater proportion of Black patients had fasting C-peptide levels >0.3 nmol/l (28% (10/36) vs. 0%, p=0.03). Of these 10 Black patients, eight were anti-GAD-negative. Thirteen Black patients (33%) were anti-GAD-positive vs. 10 (67%) White patients (p=0.03). There was no statistically significant difference in anti-GAD positivity between Black patients on oral agents or those on insulin. Most patients (5/7) admitted on oral agents had negative C-peptide levels after stabilization. Our results suggest that in patients presenting with DKA, a quarter of Black South Africans have C-peptide levels regarded as being indicative of type 2 DM and are less frequently anti-GAD-antibody-positive than are White South Africans.