CDE Monitoring Techniques 3 — Questions and Answers
Question 1: A patient's HbA1c is 6.8% but her CGM data shows frequent hypoglycemic episodes. What phenomenon explains this discordance?
- CGM sensor inaccuracy
- Glucose variability with high/low averaging (Correct answer)
- Hemoglobin variant affecting the HbA1c assay
- Incorrect CGM calibration
Correct answer: Glucose variability with high/low averaging
Alternating hyperglycemic and hypoglycemic episodes can average to a deceptively 'normal' HbA1c while masking dangerous glycemic variability.
Question 2: Which CGM metric best quantifies the degree of glucose fluctuation beyond the average level?
- Time in range (TIR)
- Coefficient of variation (CV) (Correct answer)
- Mean glucose
- GMI (glucose management indicator)
Correct answer: Coefficient of variation (CV)
Coefficient of variation (CV) measures glucose variability as a percentage of the mean; a CV ≤36% is generally considered stable.
Question 3: A continuous glucose monitor sensor placed on the abdomen shows a consistent 20–30 minute lag behind fingerstick values during rapid glucose changes. This is because:
- The sensor is malfunctioning
- CGM measures interstitial fluid glucose, which lags behind blood glucose (Correct answer)
- The sensor site has poor perfusion
- The calibration was done during a stable period
Correct answer: CGM measures interstitial fluid glucose, which lags behind blood glucose
CGM sensors measure glucose in interstitial fluid, which equilibrates with blood glucose with a physiological lag of approximately 5–15 minutes that is amplified during rapid changes.
Question 4: What is the recommended blood ketone (beta-hydroxybutyrate) threshold that should prompt a patient to seek emergency care?
- ≥0.6 mmol/L
- ≥1.0 mmol/L
- ≥1.5 mmol/L
- ≥3.0 mmol/L (Correct answer)
Correct answer: ≥3.0 mmol/L
Blood ketone levels ≥3.0 mmol/L indicate high DKA risk and warrant immediate emergency evaluation.
Question 5: A structured SMBG pattern shows consistently elevated glucose readings 2 hours after dinner but not after breakfast or lunch. What is the most appropriate clinical response?
- Increase the total daily insulin dose uniformly
- Evaluate and modify the evening meal composition and/or pre-dinner medication (Correct answer)
- Add a bedtime snack to balance the readings
- Recheck HbA1c in 3 months before making changes
Correct answer: Evaluate and modify the evening meal composition and/or pre-dinner medication
Pattern management directs intervention to the specific meal and corresponding medication or dietary factors causing the postprandial spike.
Question 6: Which type of glucose meter is MOST appropriate for a patient with sickle cell trait whose readings have been unreliable?
- A meter using glucose oxidase electrochemistry
- A photometric (colorimetric) meter
- A meter validated for hemoglobin variants and abnormal hematocrit ranges (Correct answer)
- Any FDA-cleared meter is equally appropriate
Correct answer: A meter validated for hemoglobin variants and abnormal hematocrit ranges
Hemoglobin variants and hematocrit abnormalities can interfere with some meters; selecting one validated for these conditions improves accuracy.
Question 7: During sick-day management, how frequently should a patient with type 1 diabetes check blood or urine ketones?
- Once daily in the morning
- Every 4–6 hours or whenever glucose exceeds 240 mg/dL (Correct answer)
- Only if vomiting occurs
- Every 2 hours around the clock
Correct answer: Every 4–6 hours or whenever glucose exceeds 240 mg/dL
Sick-day rules recommend checking ketones every 4–6 hours or with each high glucose reading above 240 mg/dL to detect DKA early.
CDE Monitoring Techniques 3
A patient's HbA1c is 6.8% but her CGM data shows frequent hypoglycemic episodes.
What phenomenon explains this discordance?