Yes, apart from fasting plasma glucose (FPG), postprandial glucose (PPG), and
HbA1c, another important test used in the diagnosis of
diabetes is:
Oral Glucose Tolerance Test (OGTT)
• Procedure: The patient fasts overnight, then consumes a solution containing 75 grams of glucose, and plasma glucose is measured 2 hours later.
• Diagnostic criteria:
• ≥ 200 mg/dL (11.1 mmol/L) at 2 hours = Diabetes
• 140–199 mg/dL = Impaired glucose tolerance (IGT)
• < 140 mg/dL = Normal
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Special/Additional Tests (less commonly used for diagnosis but sometimes relevant):
1. Random Plasma Glucose (RPG):
• If ≥ 200 mg/dL with classic symptoms of hyperglycemia (polyuria, polydipsia, weight loss), it is diagnostic of diabetes.
2. C-Peptide Test:
• Helps differentiate type 1 vs type 2 diabetes (low in type 1).
3. Autoantibody testing (e.g., GAD, IA2 antibodies):
• For diagnosing Type 1 diabetes or Latent Autoimmune Diabetes in Adults (LADA).
4. Fructosamine:
• Reflects average glucose over the past 2–3 weeks; useful if HbA1c is unreliable (e.g., hemoglobinopathies, recent blood loss).
5. Continuous Glucose Monitoring (CGM):
• Not used for initial diagnosis, but very useful in glycemic pattern analysis for management, especially in type 1 diabetes.