Procedures

Carbohydrate testing is all about assessing glucose levels to diagnose and monitor diabetes, while also looking for other specific sugars tied to metabolic disorders. We use a variety of techniques to get a comprehensive picture of how the body is handling sugars

Key Tests & Principles

• Glucose Measurement
  • Principle: Uses enzymatic reactions (glucose oxidase or hexokinase) to quantify glucose
  • We’re measuring the products or byproducts of these enzyme-catalyzed reactions
• Glucose Tolerance Testing (GTT)
  • Principle: Measures the body’s ability to clear glucose from the blood after a challenge dose
  • This assesses both insulin secretion and insulin sensitivity
• Glycated Hemoglobin (HbA1c)
  • Principle: Quantifies the percentage of hemoglobin that has glucose attached, reflecting average glucose levels over 2-3 months
  • Provides a long-term view of glycemic control
• Urine Glucose
  • Principle: Detects the presence of glucose in urine when blood glucose exceeds the kidney’s reabsorption capacity
  • A quick, but less sensitive, way to check for high blood sugar
• Ketone Measurement
  • Principle: Detects ketones in blood or urine, indicating fat breakdown due to insufficient glucose use
  • Important in diagnosing and monitoring diabetic ketoacidosis (DKA)
• Other Carbohydrate Tests
  • Principle: Uses specialized enzymatic or chromatographic methods to quantify other sugars like galactose or fructose
  • Used for diagnosing specific metabolic disorders

Factors Affecting Results

• Special Precautions
  • Patient Prep: Includes proper fasting, awareness of medications, and consideration of acute illness
  • Specimen Handling: Involves prompt processing, appropriate temperature control, and use of the correct anticoagulants
  • Reagent Quality: Proper storage and awareness of expiration dates are essential
• Troubleshooting
  • We need to be able to identify the source of errors (pre-analytical, analytical) if results are unexpected
• Interfering Substances
  • Substances like ascorbic acid (vitamin C), bilirubin, lipids, and hemoglobin can affect certain assays
  • Knowing about these interferences helps us choose the best methods and interpret results correctly

Interpretation & Disease Correlation

• Normoglycemia & Aberrations: Understanding normal ranges for all these tests is foundational
• Linking Labs to Disease: Recognizing how specific test patterns correlate with conditions like diabetes, prediabetes, gestational diabetes, hypoglycemia, DKA, and other metabolic disorders is the ultimate goal
• Putting in Context: Remembering that patient factors, medications, and even ethnicity can influence lab results makes interpretation more nuanced