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‐γ‐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.