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Gestational Glucose Tolerance Screening and Diagnostic Test (Two-hour, ADA Recommendations)
- Glucose Tolerance Test, Gestational (Fasting, One-hour, and Two-hour)
Screening and diagnosis of gestational diabetes
Specimen (Two-hour GGT Test)*
*A positive diagnosis requires that only one of the high thresholds be exceeded.
American Diabetes Association Standards of Medical Care in Diabetes recommendations:2
• Screen for undiagnosed type 2 diabetes at the first prenatal visit in those with risk factors using the standard nongestational diagnostic criteria.
• In pregnant women not known to have diabetes, screen for gestational diabetes mellitus (GDM) at 24 to 28 weeks of gestation using the Gestational Glucose Tolerance Screening and Diagnostic Test (Two-hour, ADA Recommendations).
• Screen women with GDM for persistent diabetes 6 to 12 weeks postpartum using nonpregnant OGTT criteria, hemoglobin A1c(102525), fasting plasma glucose (001818), or a 75-gram, two-hour oral glucose tolerance test (101200), two specimen WHO glucose tolerance test).2 Women diagnosed with GDM should, in subsequent pregnancies, be re-evaluated.
• Women with a history of GDM should have lifelong screening for the development of diabetes or prediabetes at least every three years.
Note: The American Diabetes Association (ADA) released recommendations that vary from the American College of Obstetrics and Gynecology (ACOG) recommendations. The ADA recommends the current (101000) simplified “one-step” for screening and diagnosis of gestational diabetes mellitus using a 75-gram, two-hour glucose tolerance test. The ACOG recommendations3 use a 100-gram, three-hour glucose tolerance test (102004).
Serum or plasma
1 mL serum or plasma each tube
0.5 mL serum or plasma each tube
Draw a fasting blood sample before administering glucose. Administer a 75-gram glucose and draw blood after one hour and two hours. The patient should remain seated throughout the test. Submit 1 mL serum or plasma for fasting, one-hour, and two-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 the patient's name and collection time interval (ie, fasting, one-hour, and two-hour).
Maintain specimen at room temperature.1
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, and two-hour)
|Order Code||Order Code Name||Order Loinc||Result Code||Result Code Name||UofM||Result LOINC|
|101000||Gestational 2 hour GTT||011121||Glucose, Fasting||mg/dL||1558-6|
|101000||Gestational 2 hour GTT||011122||Glucose, 1 hour||mg/dL||1507-3|
|101000||Gestational 2 hour GTT||011123||Glucose, 2 hour||mg/dL||1518-0|
|101000||Gestational 2 hour GTT||103033||Glucose (3)||N/A|