From the Guidelines
The American Diabetes Association (ADA) diagnostic criteria for diabetes include four possible methods for diagnosis, which are a fasting plasma glucose level of 126 mg/dL (7.0 mmol/L) or higher, a 2-hour plasma glucose level of 200 mg/dL (11.1 mmol/L) or higher during an oral glucose tolerance test, a hemoglobin A1C level of 6.5% (48 mmol/mol) or higher, or a random plasma glucose level of 200 mg/dL (11.1 mmol/L) or higher in a patient with classic symptoms of hyperglycemia, as stated in the most recent guidelines 1.
Diagnostic Criteria
The diagnostic criteria for diabetes are as follows:
- Fasting plasma glucose level of 126 mg/dL (7.0 mmol/L) or higher after no caloric intake for at least 8 hours
- 2-hour plasma glucose level of 200 mg/dL (11.1 mmol/L) or higher during an oral glucose tolerance test using a 75g glucose load
- Hemoglobin A1C level of 6.5% (48 mmol/mol) or higher, which should be performed in a laboratory using a method certified by the National Glycohemoglobin Standardization Program
- Random plasma glucose level of 200 mg/dL (11.1 mmol/L) or higher in a patient with classic symptoms of hyperglycemia, such as polyuria, polydipsia, polyphagia, and unexplained weight loss
Confirmation of Diagnosis
For all criteria except the random glucose with symptoms, the test should be repeated on a different day to confirm the diagnosis unless there is clear clinical evidence of hyperglycemia, as recommended by the ADA 1.
Laboratory Analysis
The diagnosis of diabetes is established by identifying the presence of hyperglycemia, and the laboratory analysis should be performed in a laboratory that is NGSP certified and standardized to the DCCT assay, as stated in the guidelines 1.
Recommendations
The ADA recommends that all asymptomatic people ≥45 years of age be screened in a healthcare setting, and an HbA1c, FPG, or 2-h OGTT evaluation is appropriate for screening, as recommended in the guidelines 1.
Summary of Key Points
- The ADA diagnostic criteria for diabetes include four possible methods for diagnosis
- The diagnostic criteria are based on the presence of hyperglycemia
- The laboratory analysis should be performed in a laboratory that is NGSP certified and standardized to the DCCT assay
- The diagnosis should be confirmed by repeat testing unless there is clear clinical evidence of hyperglycemia
- The ADA recommends screening for diabetes in asymptomatic people ≥45 years of age, as stated in the guidelines 1.
From the Research
Diagnostic Criteria for Diabetes
The diagnostic criteria for diabetes according to the ADA guidelines are not explicitly stated in the provided studies. However, the studies mention the following diagnostic measures:
- Fasting plasma glucose (FPG) 2
- Glycated hemoglobin (HbA1c) 3, 2, 4, 5, 6
- Oral glucose tolerance test (OGTT) 4, 6
- Homeostasis model assessment-estimated insulin resistance (HOMA-IR) 2
Diagnostic Thresholds
The studies mention the following diagnostic thresholds:
- HbA1c <6.5% as a target for glycemic control 3
- HbA1c ≥7% (53 mmol/mol) as a threshold for inadequate glycemic control 5
- FPG <5.5mmol/L or HbA1c <5.5% as a threshold for low-range glycemic levels 2
- FPG ≥5.5mmol/L or HbA1c ≥5.5% as a threshold for high-range glycemic levels 2
Key Findings
The studies found that:
- Lifestyle interventions, including physical activity and diet, can improve glycemic indicators in adults without impaired glucose tolerance or diabetes 2
- Pioglitazone, a thiazolidinedione, can improve post-load glucose excursions and insulin sensitivity in patients with type 2 diabetes 4, 6
- Sitagliptin and pioglitazone are equally effective in improving HbA1c levels in patients with uncontrolled type 2 diabetes on metformin and sulfonylurea 5