Diagnostic Tests for Diabetes
There is insufficient evidence to support the use of continuous glucose monitoring for screening or diagnosing prediabetes or diabetes.
In the absence of unequivocal hyperglycemia (e.g., hyperglycemic crisis), diagnosis of type 2 diabetes requires confirmatory testing, which can be a different test on the same day or the same test on a different day.
Marked discordance between A1C and repeated blood glucose measurements should raise the possibility of a problem or interference with either test.
There is insufficient evidence to support the use of continuous glucose monitoring for screening or diagnosing prediabetes or diabetes.
In the absence of unequivocal hyperglycemia (e.g., hyperglycemic crisis), diagnosis of type 2 diabetes requires confirmatory testing, which can be a different test on the same day or the same test on a different day.
Marked discordance between A1C and repeated blood glucose measurements should raise the possibility of a problem or interference with either test.
Classification
Classification of diabetes type is not always straightforward at presentation, and misdiagnosis is common.
Screening Criteria for Prediabetes and Type 2 Diabetes:
Screening for prediabetes and type 2 diabetes should be performed in asymptomatic adults with an informal assessment of risk factors or a validated risk calculator.
Informal Risk Factor Assessment for Prediabetes and Type 2 Diabetes
Additional Screening Guidelines
| Condition | Clinical Tips | Best Test |
|---|---|---|
| An altered relationship between A1C and glycemia | A mismatch between A1C and glycemia could be caused by some hemoglobin variants, pregnancy (second and third trimesters and the postpartum period), glucose-6-phosphate dehydrogenase deficiency, HIV, hemodialysis, recent blood loss or transfusion, anemia, or erythropoietin therapy. People with HIV should be screened for diabetes and prediabetes before and 3–6 months after starting or changing antiretroviral therapy, and annually if initial results are normal. | Fasting plasma glucose |
| Acute pancreatitis | Screen for diabetes 3-6 months after an episode of acute pancreatitis and annually thereafter. | Any standard test for diagnosing diabetes |
| Cystic fibrosis | Annual screening should begin by the age of 10 years in all people with cystic fibrosis not previously diagnosed with cystic fibrosis-related diabetes | Oral glucose tolerance test |
| Posttransplantation status | Screen for hyperglycemia after organ transplantation. Posttransplantation diabetes mellitus should be diagnosed when the individual is stable on immunosuppressive therapy and free of acute infections. | Oral glucose tolerance test |
| Possible monogenic diabetes | Suspect monogenic diabetes in people diagnosed with diabetes in the first 6 months of life and in children and young adults with atypical characteristics of type 1 or type 2 diabetes, who often have a family history of diabetes in successive generations (suggestive of an autosomal dominant pattern of inheritance). | Any standard test for diagnosing diabetes plus appropriate genetic testing |
| Therapy with certain medications | Consider screening people for prediabetes or diabetes if they are on certain medications known to increase diabetes risk, such as glucocorticoids, statins, thiazide diuretics, some HIV medications, and second-generation antipsychotic medications. | Any standard test test for diagnosing diabetes |
| Condition | Clinical Tips | Best Test |
|---|---|---|
| An altered relationship between A1C and glycemia | A mismatch between A1C and glycemia could be caused by some hemoglobin variants, pregnancy (second and third trimesters and the postpartum period), glucose-6-phosphate dehydrogenase deficiency, HIV, hemodialysis, recent blood loss or transfusion, anemia, or erythropoietin therapy. People with HIV should be screened for diabetes and prediabetes before and 3–6 months after starting or changing antiretroviral therapy, and annually if initial results are normal. | Fasting plasma glucose |
| Acute pancreatitis | Screen for diabetes 3-6 months after an episode of acute pancreatitis and annually thereafter. | Any standard test for diagnosing diabetes |
| Cystic fibrosis | Annual screening should begin by the age of 10 years in all people with cystic fibrosis not previously diagnosed with cystic fibrosis-related diabetes | Oral glucose tolerance test |
| Posttransplantation status | Screen for hyperglycemia after organ transplantation. Posttransplantation diabetes mellitus should be diagnosed when the individual is stable on immunosuppressive therapy and free of acute infections. | Oral glucose tolerance test |
| Possible monogenic diabetes | Suspect monogenic diabetes in people diagnosed with diabetes in the first 6 months of life and in children and young adults with atypical characteristics of type 1 or type 2 diabetes, who often have a family history of diabetes in successive generations (suggestive of an autosomal dominant pattern of inheritance). | Any standard test for diagnosing diabetes plus appropriate genetic testing |
| Therapy with certain medications | Consider screening people for prediabetes or diabetes if they are on certain medications known to increase diabetes risk, such as glucocorticoids, statins, thiazide diuretics, some HIV medications, and second-generation antipsychotic medications. | Any standard test test for diagnosing diabetes |
