Toward an Appropriate Classification of Adult-Onset Diabetes Mellitus: A Descriptive Study in Primary Care

Background: Type 2 diabetes mellitus (T2DM) is the most common form of diabetes in adults, although autoimmune reactions against pancreatic islets may also occur, leading to early insulin dependence and specific clinical features. The misclassification of autoimmune diabetes (AD) in adults has clinical implications in primary care (PC), where autoantibody testing is limited. The aim of this study was to estimate the prevalence of AD in adults at the time of diagnosis and to characterize its clinical, metabolic and lifestyle profile in comparison with that of T2DM patients. Methods: A cross-sectional study was conducted at 12 PC centers in Madrid (Spain). A total of 1006 adults aged 30 years or older who had been diagnosed with diabetes within the previous four years were included. Autoantibodies against pancreatic islets (anti-GAD65 and anti-IA-2) were analyzed in a centralized laboratory. Clinical interviews, physical examinations and reviews of electronic medical records were carried out. Results: The prevalence of AD was 7.56%. Patients with AD were younger and leaner and had more hyperglycemic symptoms and higher HbA1c levels. They had higher HDL cholesterol levels, lower triglyceride levels and more favorable cardiometabolic indices than patients with T2DM did. Patients with AD with LADA criteria differed from those with early insulin dependence. Conclusions: Autoimmune diabetes is a relatively common form of diabetes in adults and presents a clinical and metabolic profile that differs from that of T2DM. Improved recognition and targeted screening in primary care may facilitate accurate diagnosis and more appropriate therapeutic decision-making.