title: Diabetes mellitus classification.
abstract: The right classification for diabetes mellitus (DM) allows a more adequate treatment and comprises four categories: type 1 DM, type 2 DM, other types, and gestational diabetes. In some cases, there might be a superposition of situations, especially with regard to the DM that initiates in the young adult or is initially presented with diabetic ketoacidosis intermediately to type 1 and 2 DM. Thus, additions to the classic classification system have been proposed as assessing the presence of autoimmunity (antibody) and b cell function (C-peptide) to precisely define the subtypes. The aim of this literature review was to analyze these diagnostic indexes` performance in the DM classification and to describe subtypes with details. The antibodies against pancreas confirm autoimmunity, and the antibody against insulin is more accurate before 5 years old, while the anti-glutamic acid decarboxylase is more accurate after 20 years old, a test which remains positive for a longer period. The measurement of C-peptide evaluates the pancreatic insulin reserve, and the most largely used methods of stimulation are the measurement after meals or after intravenous glucagon. C-peptide values < 1.5 ng/ml define a patient with absent pancreatic function and, above this value, patients with preserved function. When the presence of antibodies (A+) directed to the pancreas is combined to its insulin secretion capability (β+), it is possible to subdivide DM`s classification in type 1A (A+β-) and 1B (A+β-); and type 2A (A+β+) and 2B (A-β+), which allows a more precise classification and treatment besides opening horizons for the understanding of DM pathogenesis.
authors.affiliation: Universidade Federal do Rio Grande do Sul, Porto Alegre, RS. jorge.voy@terra.com.br
authors.forename: Jorge de Faria
authors.initials: Jde F
authors.lastname: Maraschin
authors.forename: Nádia
authors.initials: N
authors.lastname: Murussi
authors.forename: Vanessa
authors.initials: V
authors.lastname: Witter
authors.forename: Sandra Pinho
authors.initials: SP
authors.lastname: Silveiro
mesh_terms: D001323:Autoantibodies; D015551:Autoimmunity / Q000276:immunology; D002096:C-Peptide / Q000097:blood; D003920:Diabetes Mellitus / Q000145:classification*; D005968:Glutamate Decarboxylase / Q000276:immunology*; D006801:Humans
chemical_list: D001323:Autoantibodies; D002096:C-Peptide; D005968:Glutamate Decarboxylase