Abstract
1016
Objectives: As anti-glutamic acid decardoxylase (anti-GAD) antibody is clinically utilized for the diagnosis of type 1 diabetes mellitus (DM), its role as autoimmunity level index has recently gained spotlights in the field of neurological disorders, including stiff-person syndrome, cerebellar ataxia and epilepsy. Since type 2 DM also presents pathophysiology of autoimmunity and inflammation, serum anti-GAD levels might provide diagnostic or prognostic clues. While various clinical assays measuring serum level of anti-GAD are based on diverse diagnostic technologies, the radioimmunoassay (RIA) is the most widely used conventional method as the quantitative test. Interestingly, no clinical evaluation on the association of anti-GAD level and HbA1c is present yet. Here, we collected one-year cohort of patients measured for serum anti-GAD levels in a Korean tertiary hospital.
Methods: A total of 291 adult patients with clinical impression of type 2 DM requested for anti-GAD measurement by RIA during period of one year (2020 Jan~Dec) were included in this study. HbA1c levels were measured by the Cobas Integra 800 System (Roche Diagnostics, Germany). To examine the relationship between serum anti-GAD levels and HbA1c, linear regression analysis was conducted.
Results: 48 (16.5%) patients had serum anti-GAD levels higher than limit of detection (LoD=0.7 U/mL). When cut-off value of 1.0 U/mL was applied for the positive result interpretation, 10 patients presented negative results with quantitative values (0.73~0.98 IU/mL). According to HbA1c values, 7 (14.6%), 15 (31.3%), and 22 (45.8%) patients were determined to be in active disease status of pre-diabetes, diabetes, and diabetes requiring treatment, respectively. When we divided the positive results of anti-GAD levels into weak positive (anti-GAD values of 1.0~10.0 IU/mL) and strong positive (anti-GAD values of over 10.0 IU/mL), V-shape correlation between anti-GAD and HbA1c levels was observed.
Conclusions: Quantitation of serum anti-GAD levels by RIA might provide insights into autoimmunity levels in type 2 DM patients. Differential associations between HbA1c and anti-GAD levels were observed according to anti-GAD positivity degrees.