Objective: To compare the clinical characteristics between type 2 diabetes and latent autoimmune diabetes in adults (LADA) and to define the two distinct types of LADA with different glutamic acid decarboxylase antibody (GADA) titers.
Methods: Sera of 750 patients with an initial diagnosis of type 2 diabetes mellitus (T2DM) were screened for GADA with radioimmunoprecipitation assay. The distribution and frequency of different GADA indices were described. Two hundred and ninety five patients were further studied and divided into four groups (T2DM; GADA index < 0.05; index > or = 0.5 and index > or = 0.05 but < 0.5) to compare the age of onset, body mass index, level of major component of adult hemoglobin (HbA1c) and C peptide as well as the rates of hypertension, hyperlipidemia and chronic complications.
Results: A total of 64 antibody-positive patients were identified. Compared with T2DM, these patients had younger age of onset, lower C peptide level (fasting C peptide 500 pmol/L vs 414 pmol/L, P < 0.01), lower body mass index (23.2 kg/m(2) vs 21.2 kg/m(2), P < 0.01) and also lower rates of hypertension (48.7% vs 31.7%, P < 0.05) and hyperlipidemia (60.2% vs 38.5%, P < 0.01). However, only the patients with high GADA titer had reduced beta cell function as compared with T2DM and low titer patients. Their diabetic complications were less than those of T2DM. Low GADA titer (index 0.05 - < 0.5) patients were similar to T2DM patients, except that they were prone to ketoacidemia.
Conclusion: Two clinically distinct types of LADA can be identified by GADA titers. High titer GADA (GADA > or = 0.5) patients have more resemblance to insulin dependent diabetes and can be regarded as LADA-type 1 diabetes, while low titer GADA patients (0.05 - < 0.5) have clinical and metabolic phenotype of type 2 diabetes and can be regarded as LADA-type 2 diabetes.