OGT Interpreting OGTT Results and Glucose Tolerance Classifications 2 — Questions and Answers
Question 1: What HbA1c range does the ADA use to identify prediabetes?
- 5.0%–5.6%
- 5.7%–6.4% (Correct answer)
- 6.5%–7.0%
- 7.0%–7.5%
Correct answer: 5.7%–6.4%
The ADA defines prediabetes as an HbA1c of 5.7%–6.4%, which correlates with impaired glucose tolerance found on OGTT.
Question 2: In interpreting OGTT results, a 'flat curve' with minimal glucose rise after the oral glucose load may suggest:
- Diabetes mellitus
- Malabsorption or delayed gastric emptying (Correct answer)
- Reactive hypoglycemia
- Cushing's syndrome
Correct answer: Malabsorption or delayed gastric emptying
A flat OGTT curve indicates minimal glucose absorption after the oral load, which may result from malabsorption or delayed gastric emptying.
Question 3: Reactive hypoglycemia on an extended OGTT is characterized by:
- Fasting glucose below 50 mg/dL
- A normal initial glucose rise followed by a drop below 70 mg/dL at 2–3 hours (Correct answer)
- Persistently elevated glucose throughout the test
- No measurable glucose peak after the load
Correct answer: A normal initial glucose rise followed by a drop below 70 mg/dL at 2–3 hours
Reactive hypoglycemia shows a normal or exaggerated early glucose rise, followed by excessive insulin secretion causing glucose to drop below 70 mg/dL at 2–3 hours.
Question 4: For a 3-hour 100g OGTT using Carpenter-Coustan criteria, gestational diabetes is diagnosed when how many values meet or exceed thresholds?
- 1 out of 4
- 2 out of 4 (Correct answer)
- 3 out of 4
- All 4 values
Correct answer: 2 out of 4
Per Carpenter-Coustan criteria, gestational diabetes is diagnosed when 2 or more of the 4 measured values (fasting, 1-hour, 2-hour, 3-hour) meet or exceed established thresholds.
Question 5: What is the fasting plasma glucose threshold in the Carpenter-Coustan criteria for the 3-hour 100g OGTT?
- 90 mg/dL
- 95 mg/dL (Correct answer)
- 105 mg/dL
- 110 mg/dL
Correct answer: 95 mg/dL
The Carpenter-Coustan criteria set the fasting threshold at 95 mg/dL, which is lower than the older NDDG (O'Sullivan) criteria value of 105 mg/dL.
Question 6: Which OGTT glucose curve pattern is most consistent with impaired first-phase insulin secretion seen in early type 2 diabetes?
- Flat curve with minimal glucose rise
- Normal fasting and normal 2-hour glucose
- Delayed glucose peak at 2 hours with slow return to baseline (Correct answer)
- Immediate drop in glucose below fasting levels
Correct answer: Delayed glucose peak at 2 hours with slow return to baseline
Early type 2 diabetes typically shows a delayed and exaggerated glucose peak due to impaired first-phase insulin secretion, with slow return to baseline reflecting insulin resistance.
Question 7: An exaggerated early glucose peak at 30–60 minutes that returns fully to normal by 2 hours on an OGTT most likely suggests:
- Diabetes mellitus
- Dumping syndrome or accelerated gastric emptying (Correct answer)
- Adrenal insufficiency
- Chronic renal failure
Correct answer: Dumping syndrome or accelerated gastric emptying
An exaggerated early peak with rapid return to normal suggests accelerated gastric emptying or dumping syndrome, causing rapid glucose absorption followed by a brisk insulin response.
OGT Interpreting OGTT Results and Glucose Tolerance Classifications 2
What HbA1c range does the ADA use to identify prediabetes?