Carboxypeptidase‐H Autoantibodies Differentiate a More Latent Subset of Autoimmune Diabetes from Phenotypic Type 2 Diabetes among Chinese Adults

Abstract

This study aimed to investigate whether carboxypeptidase-H antibody (CPH-Ab) can help identify latent autoimmune diabetes in adults (LADA). Phenotypic type 2 diabetic (T2D) patients (n= 1296) were studied for CPH Abs and autoantibodies to glutamic acid decarboxylase (GAD-Abs). CPH-Ab(+) T2D patients also underwent testing for insulinoma protein tyrosine phosphatase (IA-2A). Clinical features were compared among CPH-Ab(+), GAD-Ab(+), and Ab(-) T2D patients. Some of the antibody-positive patients were followed up for 3 years to assess beta cell function. The prevalence of CPH-Abs in T2D patients was 4.8%, significantly higher than that in controls. Double positivity was rare between CPH-Abs and GAD-Abs or IA-2A. Compared to patients with Ab(-) T2D, those with CPH-Ab(+) T2D had lower BMI, lower fasting C-peptide (FCP) levels, and more frequent ketosis, while not as much as did those with GAD-Ab(+) T2D. The mild beta cell dysfunction in patients with CPH-Ab(+) T2D was associated with their longer duration of diabetes. No marked change of C-peptide in the CPH-Ab(+) group was found during follow-up. These findings demonstrated that CPH-Abs may allow discrimination of a more latent subset of adult-onset autoimmune diabetes (LADA) whose features are intermediate between those with classic GAD-Ab(+) LADA and patients with Ab(-) T2D.