Abstract:

Objective To investigate the proportion of latent autoimmune diabetes in adult（LADA） in patients with type 2 diabetes mellitus（T2DM） and the clinical significance of C peptide and related biochemical indices. Methods Serum islet cell antibody（ICA）,tyrosine phosphatase antibody（IA-2A）,glutamic acid decarboxylase antibody（GADA） and insulin antibody（IAA） were determined in 406 patients diagnosed as T2DM for the diagnosis of LADA,and the results were compared with blood glucose,glycated hemoglobin A_1c（HbA_1c）,C peptide and related biochemical indices. The cut-off values of fasting C peptide and postprandial 2 h C peptide were chosen by receiver operating characteristic（ROC） curve to differentiate LADA and T2DM. Results In 406 T2DM patients,39 cases were diagnosed as LADA（9.61%）. In LADA patients,fasting blood glucose was（13.5±10.5） mmol/L,postprandial 2 h blood glucose was（15.2±11.5） mmol/L,HbA_1c was（10.2±2.5）%,and those in non-LADA T2DM patients were（10.1±8.9） mmol/L,（12.5±11.5） mmol/L and（7.8±2.6）%,which decreased significantly（P<0.05）. In LADA patients,fasting C peptide was（0.45±0.25） μg/L,postprandial 2 h C peptide was（1.05±0.26） μg/L,which were lower than those in non-LADA T2DM patients [（1.35±0.55） μg/L and（4.12±2.25） μg/L,P<0.05]. The optimal cut-off values of fasting C peptide and postprandial 2 h C peptide for differentiating LADA and T2DM were 0.865 and 1.595 μg/L. The sensitivities of fasting C peptide and postprandial 2 h C peptide for the diagnosis of LADA were 97.4% and 99.5%,and the specificities were 100.0% and 100.0%. Conclusions In the clinical diagnosis of T2DM,insulin autoantibodies can be determined for LADA patients,and fasting C peptide and postprandial 2 h C peptide can be used as indices for the differential diagnosis of LADA and T2DM.

Key words: Insulin autoantibody, Glycated hemoglobin A1c, C peptide, Latent autoimmune diabetes in adult, Type 2 diabetes mellitus