Diagnostic value of combined islet antigen-reactive T cells and autoantibodies assays for type 1 diabetes mellitus

Aims/Introduction Type 1 diabetes mellitus is a T cell-mediated autoimmune disease. However, the determination of the autoimmune status of type 1 diabetes mellitus relies on islet autoantibodies (Abs), as T-cell assay is not routinely carried out. This study aimed to investigate the diagnostic value of combined assay of islet antigen-specific T cells and Abs in type 1 diabetes mellitus patients. Materials and Methods A total of 54 patients with type 1 diabetes mellitus and 56 healthy controls were enrolled. Abs against glutamic acid decarboxylase (GAD), islet antigen-2 and zinc transporter 8 were detected by radioligand assay. Interferon-gamma-secreting T cells responding to glutamic acid decarboxylase 65 and C-peptide (CP) were measured by enzyme-linked immunospot. Results The positive rate for T-cell responses was significantly higher in patients with type 1 diabetes mellitus than that in controls (P < 0.001). The combined positive rate of Abs and T-cell assay was significantly higher than that of Abs assay alone (85.2% vs 64.8%, P = 0.015). A significant difference in fasting CP level was found between the T+ and T- groups (0.07 +/- 0.05 vs 0.11 +/- 0.09 nmol/L, P = 0.033). Furthermore, levels of fasting CP and postprandial CP were both lower in the Ab(-)T(+) group than the Ab(-)T(-) group (fasting CP 0.06 +/- 0.05 vs 0.16 +/- 0.12 nmol/L, P = 0.041; postprandial CP 0.12 +/- 0.13 vs 0.27 +/- 0.12 nmol/L, P = 0.024). Conclusions Enzyme-linked immunospot assays in combination with Abs detection could improve the diagnostic sensitivity of autoimmune diabetes.