Gestational Diabetes Screen (ACOG Recommendations)
Also known as: Glucose Tolerance, Gestational Diabetes (One-hour)
Use
Screening test for gestational diabetes
Special Instructions
The patient is not required to be fasting for this test. A 50-gram oral glucose load is administered, followed by plasma glucose determination one hour later. Ensure the patient remains seated and refrains from smoking during the test. Gray-top tubes may be submitted without centrifugation. Label the tube with the patient's name and collection time interval. Additional time may be necessary for reflex or confirmatory testing, and testing schedules may vary.
Limitations
The screening test is not definitive for diagnosing diabetes mellitus and should not be used in patients with a known history of diabetes mellitus. The test requires adherence to specific collection instructions for accurate results. A glucose threshold of >139 mg/dL identifies approximately 80% of women with GDM, but sensitivity increases to 90% with a threshold >129 mg/dL. Results must be interpreted in the context of clinical history and in conjunction with confirmatory tests.
Methodology
Automated Analyzer (Clinical Chemistry)
Biomarkers
LOINC Codes
- 1504-0
- 1504-0
Result Turnaround Time
1 day
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
1 mL serum or plasma each tube
Minimum Volume
0.5 mL serum or plasma each tube
Container
Gel-barrier tube or gray-top (sodium fluoride/potassium oxalate plasma) tube
Collection Instructions
Draw one-hour specimen after a 50-gram glucose challenge. Submit 1 mL serum or plasma for one-hour specimen. Separate serum or plasma from cells within 45 minutes of venipuncture. Gray-top tubes may be submitted without centrifugation.
Patient Preparation
None; glucose challenge is administered without regard to time of day or time of last meal.
Storage Instructions
Maintain specimen at room temperature.
Causes for Rejection
Frozen gray-top tube (frozen plasma from gray-top is acceptable); stressed patient (surgery, infection, corticosteroids) should not have GTT; specimen not labeled with collection time intervals (i.e., one hour)
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 14 days |
| Refrigerated | 14 days |
| Frozen | 14 days |