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Print CPT 82951; 82952
Synonyms
- Glucose Tolerance, Gestational Diabetes (Fasting, One-hour, Two-hour, and Three-hour)
Test Details
Turnaround Time
Within 1 day
Use
Diagnose gestational diabetes
Special Instructions
The ADA 2011 standards1 vary from the ACOG recommendations.2 See Additional Information below.
Test Includes
100-g glucose load; plasma glucose measured fasting, and at one, two, and three hours
Methodology
Enzymatic
Additional Information
In 2013,2 the American College of Obstetricians and Gynecologists (ACOG) recommended that all pregnant women be screened for gestational diabetes mellitus (GDM)—whether by patient history, clinical risk factors, or with a 50-gram, one-hour loading test at 24 to 28 weeks of gestation to determine blood glucose levels—and suggested relying on the result of the 100-gram, three-hour oral glucose tolerance test for diagnosis (often referred to as a "two-step" method).
The American Diabetes Association (ADA)1 released standards that vary from the ACOG recommendations. The ADA standards recommend a simplified "one-step" approach to the screen and diagnosis of gestational diabetes mellitus with a 75-gram, two-hour glucose tolerance test. The Labcorp test according to the ADA recommendations is Gestational Glucose Tolerance Screening and Diagnostics Test (Two-hour, ADA Recommendations) [101000].
Specimen Requirements
Information on collection, storage, and volume
Specimen
Serum or plasma
Volume
1 mL serum or plasma each tube
Minimum Volume
0.5 mL serum or plasma each tube
Container
Gel-barrier tubes (4) or gray-top (sodium fluoride/potassium oxalate plasma) tubes (4)
Storage Instructions
Maintain specimen at room temperature.3
Causes for Rejection
Frozen gray-top tube (frozen plasma from gray-top is acceptable); stressed patient (surgery, infection, corticosteroids) should not have GTT; specimens not labeled with collection time intervals (i.e., fasting, one-hour, two-hour, and three-hour)
Collection
Draw a fasting blood sugar before administering 100-gram glucose, and draw blood at one, two, and three hours. The subject should remain seated and not smoke throughout the test. Submit 1 mL serum or plasma for fasting, one-hour, two-hour, and three-hour specimens. Separate serum or plasma from cells within 45 minutes of venipuncture. Gray-top tubes only, may be submitted without centrifugation. Label each tube with patient's name and collection time interval (i.e., fasting, one-hour, two-hour, and three-hour).