From the Guidelines
The oral glucose challenge test ranges are 92-153 mg/dL for a 75-g test and 95-180 mg/dL for a 100-g test, with specific cutoffs at 92 mg/dL (fasting), 180 mg/dL (1 hour), and 153 mg/dL (2 hours) for the 75-g test, and 95 mg/dL (fasting), 180 mg/dL (1 hour), 155 mg/dL (2 hours), and 140 mg/dL (3 hours) for the 100-g test 1.
Key Points
- The 75-g oral glucose tolerance test (OGTT) is performed with plasma glucose measurements at fasting, 1 hour, and 2 hours, with cutoffs of 92 mg/dL (fasting), 180 mg/dL (1 hour), and 153 mg/dL (2 hours) 1.
- The 100-g OGTT is performed with plasma glucose measurements at fasting, 1 hour, 2 hours, and 3 hours, with cutoffs of 95 mg/dL (fasting), 180 mg/dL (1 hour), 155 mg/dL (2 hours), and 140 mg/dL (3 hours) 1.
- The 50-g glucose challenge test (GCT) is used as an initial screening, with a cutoff of 130-140 mg/dL to determine the need for a subsequent OGTT 1.
Testing Approaches
- A one-step approach involves performing a diagnostic OGTT, while a two-step approach involves an initial screening with a 50-g GCT, followed by a diagnostic OGTT if the screening result exceeds the threshold value 1.
- The choice of testing approach and threshold values may vary depending on individual risk factors and clinical guidelines 1.
From the Research
Ranges for Oral Glucose Challenge Test
The oral glucose challenge test is a widely used screening method for gestational diabetes mellitus. The following are the ranges for the oral glucose challenge test:
- A threshold of 140 mg/dL is commonly used, with sensitivity and specificity ranging from 70% to 88% and 69% to 89%, respectively 2, 3.
- A lower threshold of 130 mg/dL has also been suggested, with sensitivity and specificity ranging from 88% to 99% and 66% to 77%, respectively 3.
- The American College of Obstetricians and Gynecologists recommends a 2-step protocol, with a 50-g glucose challenge at 24 to 28 weeks' gestation, followed by a 100-g oral glucose tolerance test if the screening test threshold is exceeded 4.
- The International Association of Diabetes and Pregnancy Study Groups recommends a 1-step approach, with a diagnostic 75-g, 2-hour oral glucose tolerance test 4.
Threshold Values
The following threshold values have been suggested for the oral glucose challenge test:
- 140 mg/dL: This is the most commonly used threshold, with a sensitivity and specificity of 70% to 88% and 69% to 89%, respectively 2, 3.
- 130 mg/dL: This threshold has been suggested as an alternative, with a sensitivity and specificity of 88% to 99% and 66% to 77%, respectively 3.
- 136 mg/dL: This threshold has been suggested for use with the Carpenter-Coustan criteria, with a sensitivity and specificity of 70% to 88% and 69% to 89%, respectively 2.
Test Characteristics
The oral glucose challenge test has the following test characteristics: