Gestational Diabetes Evaluation
Glucose Tolerance, Gestational Diabetes (One-hour)
Screening test for gestational diabetes
The ADA recommends a simplified “one-step” approach to the screen and diagnosis of gestational diabetes mellitus with a 75-gram, two-hour glucose tolerance test. The test according to the ADA recommendations is Gestational Glucose Tolerance Screening and Diagnostics Test (Two-hour, ADA Recommendations) . A glucose tolerance screen glucose threshold >139 mg/dL after a 50-gram load identifies approximately 80% of women with gestational diabetes mellitus, while the sensitivity is further increased to approximately 90% by a threshold >129 mg/dL. Perform a diagnostic 100-gram oral glucose tolerance test (102004) on a separate day on women who exceed the chosen threshold on 50-gram screening.
Serum or plasma
1 mL serum or plasma each tube
Gel-barrier tube or gray-top (sodium fluoride/potassium oxalate plasma) tube
None; glucose challenge is administered without regard to time of day or time of last meal.
A fasting blood sample is not required. Draw one hour specimen after a 50-gram glucose challenge. The patient should remain seated and not smoke throughout the test. Submit 1 mL serum or plasma for one-hour specimen. Separate serum or plasma from cells within 45 minutes of venipuncture. Gray-top tubes only, may be submitted without centrifugation. Label tube with patient’s name and collection time interval (ie, one-hour).
Maintain specimen at room temperature.
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)
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