Newly diagnosed latent autoimmune diabetes in adults (LADA) is associated with low level glutamate decarboxylase (GAD65) and IA-2 autoantibodies

A quantitative assay with microSepharose was used to determine GAD65Ab and IA-2Ab levels in 771 population-based patients diagnosed with diabetes mell itus at 15 to 34 years of age, and in 828 matched controls. Among the patie nts, 587 (76%) were classified with type I, 108 (14%) with type III, and 76 (10%) with unclassifiable diabetes. The levels above normal demonstrated a prevalence of GAD65Ab in 66% of type I diabetes, 50% of type II diabetes a nd 54% of unclassifiable patients and for IA-2Ab in 40%, 17% and 21%, respe ctively. Among the autoantibody-positive sera, the LADA patients had a lowe r GAD65Ab index (median 0.19, p <0.0001) and IA-2Ab index (median 0.28, p < 0.0001) than the type I patients (median 0.37 and 0.66). Patients with uncl assifiable diabetes had a GAD65Ab (median 0.43) or IA-2Ab (median 0.63) ind ex which was not different from the type I diabetes patients. Our data demo nstrate that young adult new-onset LADA patients have low level GAD65Ab and IA-2Ab. The low-level autoantibodies may signify a less aggressive beta-ce ll autoimmunity, which may explain why these patients are often classified with type II or non-insulin-dependent diabetes.