Role of anti-GAD, anti-IA2 antibodies and C-peptide in differentiating latent autoimmune diabetes in adults from type 2 diabetes mellitus

Latent autoimmune diabetes in adults (LADA) is a form of autoimmune diabetes affecting adult patients who do not require insulin at diagnosis, positive for circulating islet autoantibodies and characterized by slower beta cell destruction. The study was aimed to identify and characterize LADA patients from clinically diagnosed type 2 diabetes mellitus (DM). We estimated anti-glutamic acid decarboxylase (anti-GAD), anti-tyrosine phosphatase-like insulinoma antigen 2 (anti-IA2) antibodies, fasting connecting peptide (C-peptide) and other clinical and biochemical parameters in 297 clinically diagnosed type 2 DM patients. The diagnosis of LADA was made by the presence of at least one pancreatic autoantibody, and thereafter LADA groups were compared with those of autoantibody-negative type 2 DM groups. The prevalence of LADA was found to be 15.2 % among patients presumed to have type 2 DM. There was significant difference concerning age of patients (p < 0.001), body mass index (p < 0.001), serum levels of C-peptide (p < 0.001), insulin (p < 0.001), total cholesterol (p < 0.001), triglycerides (p = 0.025), high-density lipoprotein cholesterol (HDL-C; p = 0.004), low-density lipoprotein cholesterol (LDL-C; p = 0.001) as well as insulin resistance (p < 0.001) between LADA group and type 2 DM patients. In conclusion, anti-GAD antibody and C-peptide level determination can be considered as confirmatory diagnostic markers for LADA, along with anti-IA2 assay, while other clinical and biochemical parameters can be useful for further characterizing LADA patients.