What are the ADA diagnostic criteria for type 1 diabetes mellitus (DM)?

Updated: Jul 08, 2020
  • Author: Samuel T Olatunbosun, MD, FACP, FACE; Chief Editor: George T Griffing, MD  more...
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According to the 2019 American Diabetic Association (ADA) guidelines, the following diagnostic criteria are required for the three stages of type 1 diabetes [4] :

  • Stage 1: multiple autoantibodies; no impaired glucose tolerance (IGT) or impaired fasting glucose (IFG)
  • Stage 2: multiple autoantibodies; dysglycemia (IFG and/or IGT); fasting plasma glucose (FPG) of 100-125 mg/dL (5.6-6.9 mmol/L); 2-hour  plasma glucose (PG) of 140-199 mg/dL (7.8-11.0 mmol/L); HBA1C of 5.7%-6.4% (39-47 mmol/mol) or ≥10% increase in HBA1C
  • Stage 3: clinical symptoms; diabetes by standard criteria
  • Use plasma glucose rather than HBA1C to diagnose the acute onset of type 1 diabetes in those with hyperglycemia symptoms
  • The persistence of two or more autoantibodies predicts clinical diabetes and may indicate intervention is needed in the setting of a clinical trial

One of the following criteria must be met for a diagnosis of diabetes [4] :

  • FPG ≥126 mg/dL (7.0 mmol/L), OR 
  • 2-hour PG ≥200 mg/dL (11.1 mmol/L) during an oral glucose tolerance test (OGTT), OR
  • HBA1C ≥6.5% (48 mmol/mol), OR
  • Random plasma glucose ≥200 mg/dL (11.1 mmol/L) in a patient with classic symptoms of hyperglycemia or hyperglycemic crisis

To avoid misdiagnosis or missed diagnosis, perform HBAIC testing with  a method that is certified by the NGSP and standardized to the Diabetes Control and Complications Trial (DCCT) assay. [4]

In the presence of marked discordance between measured and plasma glucose levels of HBA1C, consider the possibility of HBA1C assay interference from hemoglobin variants (ie, hemoglobinopathies), and consider use of an assay without interference or plasma glucose criteria to diagnose diabetes. [4]  Use only plasma glucose criteria to diagnose diabetes in the setting of conditions associated with an altered relationship between HBA1C and glycemia (eg, sickle cell disease, second and third pregnancy trimesters and the postpartum period, glucose-6-phosphate dehydrogenase deficiency, infection with human immunodeficiency virus, hemodialysis, recent blood loss or transfusion, or erythropoietin therapy). [4]

If unequivocal hyperglycemia is absent, the diagnosis requires two abnormal test results from the same sample or in two separate test samples. [4]

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