LADA and CARDS: A Prospective Study of Clinical Outcome in Established Adult-Onset Autoimmune Diabetes

OBJECTIVE: Diabetes-associated autoantibodies can be detected in adult-onset diabetes, even when initially non-insulin requiring, i.e., with latent autoimmune diabetes. We aimed to identify adult-onset autoimmune diabetes in patients with established "type 2 diabetes" participating in the Collaborative Atorvastatin Diabetes Study (CARDS) to characterize their phenotype and clinical outcome. RESEARCH DESIGN AND METHODS: We prospectively studied 2,425 European patients with presumed type 2 diabetes (mean age 62 years, diabetes duration 7.9 years) for outcomes at 3.9 years after randomization to either atorvastatin or placebo. Subjects were screened for autoantibodies to GAD (GADA), insulinoma-associated antigen-2 (IA-2A), and zinc-transporter 8 (ZnT8A). RESULTS: A total of 173 patients (7.1%) had GADA, of whom 11 (0.5%) and 5 (0.2%) were also positive for IA-2A and ZnT8A, respectively. At baseline, 44% of GADA-positive patients were not on insulin. Fewer autoantibody-positive than autoantibody-negative patients had metabolic syndrome (64 vs. 80%), and more were on insulin (56 vs. 17%) (P < 0.0001 for each) without lower HbA1c (69 mmol/mol 8.5% vs. 62 mmol/mol 7.8%). The frequency of microvascular and macrovascular events was similar in both cohorts, independent of atorvastatin. CONCLUSIONS: Adult-onset autoimmune diabetes was prevalent, even in patients with established diabetes presumed to have type 2 diabetes. After 11.8 years' diabetes duration, nearly half the patients with autoimmune diabetes were not on insulin treatment and almost two-thirds had metabolic syndrome. The type of diabetes, whether autoimmune diabetes or type 2 diabetes, did not impact the risk of microvascular disease.