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

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.