What are the diagnostic criteria and treatment options for Type 2 Diabetes?

Diagnostic Criteria and Treatment Options for Type 2 Diabetes

Type 2 diabetes is diagnosed when any one of the following criteria is met: fasting plasma glucose ≥126 mg/dL, 2-hour plasma glucose ≥200 mg/dL during an oral glucose tolerance test, A1C ≥6.5%, or random plasma glucose ≥200 mg/dL with classic symptoms of hyperglycemia. 1, 2

Diagnostic Criteria

Primary Diagnostic Tests

• Fasting Plasma Glucose (FPG) ≥126 mg/dL (7.0 mmol/L), with fasting defined as no caloric intake for at least 8 hours 1, 2
• 2-hour Plasma Glucose ≥200 mg/dL (11.1 mmol/L) during a 75-g oral glucose tolerance test (OGTT) 1, 2
• Hemoglobin A1C ≥6.5% (48 mmol/mol), performed in a laboratory using a method certified by the National Glycohemoglobin Standardization Program (NGSP) 1, 2
• Random Plasma Glucose ≥200 mg/dL (11.1 mmol/L) in a patient with classic symptoms of hyperglycemia (polyuria, polydipsia, unexplained weight loss) 1, 2

Confirmation Requirements

• In the absence of unequivocal hyperglycemia with acute metabolic decompensation, diagnosis requires two abnormal test results from the same sample or in two separate test samples 1
• If using two different tests and both are above diagnostic thresholds, the diagnosis is confirmed 1
• If results are discordant from two different tests, the test with results above the diagnostic threshold should be repeated 1
• No confirmation is needed when a patient has classic symptoms of hyperglycemia with a random plasma glucose ≥200 mg/dL 1, 2

Prediabetes Criteria

• Fasting Plasma Glucose: 100-125 mg/dL (5.6-6.9 mmol/L) - Impaired Fasting Glucose (IFG) 1, 2
• 2-hour Plasma Glucose: 140-199 mg/dL (7.8-11.0 mmol/L) - Impaired Glucose Tolerance (IGT) 1, 2
• A1C: 5.7-6.4% (39-47 mmol/mol) 1, 2

Screening Recommendations

Who to Screen

• Adults aged 45 years and older 3
• Overweight or obese adults (BMI ≥25 kg/m² or ≥23 kg/m² in Asian Americans) with one or more risk factors at any age 3
• Risk factors include: family history of diabetes, high-risk race/ethnicity (African American, American Indian, Hispanic/Latino, Asian American), history of cardiovascular disease, hypertension, HDL <35 mg/dL and/or triglycerides >250 mg/dL, physical inactivity, and conditions associated with insulin resistance 3, 4
• Women with prior gestational diabetes mellitus 3

Screening Frequency

• If results are normal, repeat testing at minimum of 3-year intervals 5
• More frequent testing may be appropriate depending on initial results and risk status 5

Special Considerations for Testing

A1C Testing Limitations

• A1C should not be used for diagnosis in conditions affecting red blood cell turnover, including: 1, 2
  • Hemoglobinopathies
  • Hemolytic anemias
  • Pregnancy (second and third trimesters)
  • Recent blood loss or transfusion
  • Hemodialysis
  • Erythropoietin therapy
• In these conditions, only plasma glucose criteria should be used 1, 2
• Marked discordance between measured A1C and plasma glucose levels should raise the possibility of hemoglobin variants interfering with the assay 1, 2

Treatment Options for Type 2 Diabetes

Lifestyle Modifications

• Weight management through diet and physical activity is a cornerstone of treatment 4
• Physical activity can reduce hemoglobin A1C by 0.4% to 1.0% and improve cardiovascular risk factors 4

Pharmacological Treatment

• First-line medications: 4

  • Metformin is generally the first-line therapy for most patients with type 2 diabetes
  • For patients with cardiovascular or kidney comorbidities or at high cardiovascular risk, consider glucagon-like peptide-1 receptor agonists (GLP-1RAs) or sodium-glucose cotransporter 2 inhibitors (SGLT2is)

• Common add-on medications: 4

  • Dual glucose-dependent insulinotropic polypeptide (GIP)/GLP-1RAs
  • Dipeptidyl peptidase-4 inhibitors
  • Sulfonylureas
  • Thiazolidinediones

• Insulin therapy: 4

  • Approximately one-third of patients with type 2 diabetes require insulin during their lifetime

Benefits of Specific Medications

• SGLT2i and GLP-1RA medications have demonstrated benefits compared to placebo: 4
  • 12%-26% risk reduction for atherosclerotic cardiovascular disease
  • 18%-25% risk reduction for heart failure
  • 24%-39% risk reduction for kidney disease
• High-potency GLP-1RA and dual GIP/GLP-1RA medications result in weight loss of >5% in most individuals with type 2 diabetes, and weight loss may exceed 10% 4

Clinical Pearls and Pitfalls

Important Considerations

• Type 2 diabetes accounts for 90-95% of all diabetes cases 1, 4
• Early diagnosis is crucial to prevent complications related to chronic hyperglycemia 1
• Even undiagnosed patients are at increased risk of developing macrovascular and microvascular complications 3, 4
• The concordance between FPG, 2-h PG, and A1C tests is imperfect; they do not necessarily detect diabetes in the same individuals 1
• Insulin resistance may improve with weight reduction and/or pharmacologic treatment but is seldom restored to normal 3

Common Pitfalls to Avoid

• Relying solely on A1C for diagnosis in conditions affecting red blood cell turnover 1, 2
• Failing to confirm diagnosis with a second test when required 1
• Overlooking the need for screening in high-risk populations, particularly those with BMI ≥23 kg/m² in Asian Americans 3
• Misdiagnosis of diabetes type, which can occur in up to 40% of adults with new type 1 diabetes who are misdiagnosed as having type 2 diabetes 3