Diagnostic criteria and classification of diabetes

Diabetes, a group of complex metabolic disorders, remains a major health problem in the twenty-first century. The unabated increasing rate of type 2 diabetes (T2DM) and obesity appears to be plateauing in the U.S.A. The incidence of the less common type 1 diabetes (T1DM) has also increased at a slower pace. Diabetes in children and adolescents, however, has accelerated and evolved into a heterogeneous condition that is more closely related to T2DM. The landscape of diabetes has changed dramatically in the past few decades. The knowledge gained from many large clinical trials and new drug development has led to a better understanding of the pathophysiology and treatment of each of the disease states. Diabetes remains characterized by elevated glycemic markers and distinctive complications. Better diagnosis and earlier treatment has resulted in fewer complications, but major challenges remain as the target guidelines are unmet in approximately half of the U.S. adult population, particularly among younger individuals in more susceptible ethnic and racial groups. In this chapter we review the classification and diagnosis of the major types of diabetes. A well-established set of criteria is continuously revised to reflect current knowledge of the disease. Screening high-risk individuals has allowed for earlier diagnosis and patientcentered interventions to prevent complications. Fewer people now live with undiagnosed disease. While glycemic markers remain the gold standard for treatment and diagnosis, that advances in genetics and metabolomics will soon be used to better define and manage these conditions. Due to the higher prevalence of obesity and diabetes in the young, diabetes in pregnancy is now found not only in those with established T1DM but also in those with T2DM. An increasing rate of women are diagnosed with diabetes during their pregnancy. Updated recommendations provide better methods and criteria for screening and diagnosis. We hope that this chapter helps to elucidate current and well-established criteria to screen high-risk individuals, allowing for both an earlier diagnosis as well as better patient-centered interventions to prevent future complications of this disease.