Glutamic acid decarboxylase 65 autoantibody levels discriminate two subtypes of latent autoimmune diabetes in adults.

OBJECTIVE: To compare the clinical characteristics between type 2 diabetes mellitus (T2DM) and latent autoimmune diabetes in adults (LADA) with different titers of glutamic acid decarboxylase autoantibody (GADA) and to define the two distinct subtypes of LADA.
METHODS: Sera of 750 patients with an initial diagnosis of T2DM from central south of China were screened for GADA using a radioligand assay. The distribution and frequency of GADA levels were described. Two hundred and ninety-five patients were divided into the T2DM group (n = 233) and the LADA group (n = 62) to compare the age of onset, body mass index, HbA(1c), C-peptide, hypertension, dyslipidemia and chronic diabetic complications. Furthermore, LADA patients with different GADA titers were subdivided to analyze the same indexes as the above.
RESULTS: The prevalence of LADA (defined as GADA > or = 0.05, namely GADA positive) was 9.7% in the 750 initially diagnosed type 2 diabetic patients. Compared with T2DM, LADA patients were younger at their ages of onset, had lower C-peptide and body mass index, and also had less cases with hypertension and with dyslipidemia. However, only patients with high titer of GADA had poorer beta cell functions and less diabetic complications compared to T2DM and low GADA titer of LADA patients. Patients with low GADA titer were similar to T2DM patients, except that they were prone to develop ketosis more frequently.
CONCLUSIONS: Two clinically distinct subtypes of LADA can be identified by GADA levels in patients initially-diagnosed as type 2 diabetes. Patients with high titer of GADA (GADA > or = 0.5) subsequently develop more insulin dependency, which are classified as LADA-type 1; while those with lower GADA titer (0.05 < or = GADA < 0.5) and having clinical and metabolic phenotypes of type 2 diabetes are classified as LADA-type 2.