The IHS Division of Diabetes supports the ADA recommendations for the diagnosis of type 2 diabetes.
There are four methods to dx diabetes; for methods one through three, unless unequivocal hyperglycemia, confirm dx with a second test on a separate day:
- A1C ≥6.5% (preferred method)
- Fasting plasma glucose ≥126 mg/dL
- 2-hour plasma glucose ≥200 mg/dL during an oral glucose tolerance test (OGTT) using a 75 g oral glucose load
- Random plasma glucose ≥200 mg/dL plus symptoms of diabetes: e.g., polyuria, polydypsia, or unexplained weight loss
Categories of Increased Risk for Diabetes (“Prediabetes”) are defined as any of the following:
- A1C 5.7 to 6.4%
- Fasting plasma glucose 100-125 mg/dL
- 2-hour plasma glucose of 140-199 mg/dL during a 75 g OGTT
How to use A1C for diagnosis:
- Ensure that A1C is clearly and accurately listed in EHR or other local medical record.
- Can screen with a point of care (POC) A1C test, however ADA recommends that laboratory-run tests be used to diagnose diabetes.
- If A1C test is ≥6.5%, repeat A1C test to confirm.
- If get two tests (e.g. A1C and FPG) and one is in the diagnostic range and the other isn’t, what do you do?
- Repeat the test which was in the diagnostic range and base the diagnostic decision on the basis of the confirmed test.
- If get two tests (e.g. A1C and FPG) and both are significantly elevated, it's not necessary to confirm with a repeat test of either if it fits the clinical picture.
When not to use A1C for diagnosis:
- Hemoglobinopathies—HbS, HbC, HbF, HbE may interfere with some A1C assays.
- Variation in red blood cell lifespan (e.g. hemolysis, blood loss, blood transfusions).
Who should be tested for diabetes/prediabetes (non-pregnant asymptomatic patients)
- Adults: overweight or obese (BMI ≥25) and/or strong family history of type 2 diabetes in 1st or 2nd degree relative and/or history of gestational diabetes (GDM).
- Children: >10 years of age (or earlier if entered puberty)
- If BMI >85th %ile and any of the following:
- Family history of type 2 diabetes in 1st or 2nd degree relative, or
- Presence of a condition associated with insulin resistance [Acanthosis nigricans, Hypertension, Dyslipidemia, Polycycstic Ovarian Syndrome (PCOS)], or
- Maternal history of pre-existing or gestational diabetes during child’s gestation