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Test Code GGTT Glucose Gestational Tolerance Test

Important Note

A fasting glucose will be performed before the glucose beverage is given. If the fasting glucose is > 140 mg/dL the patients physician will be notified to decide if the test will be continued.

Performing Laboratory

Memorial Hospital Laboratory- Automated Procedures  304-388-5953       
General Hospital Laboratory 304-388-6244
Women and Children's Hospital Laboratory 304-388-2385
Teays Valley Hospital Laboratory 304-757-1770
Greenbrier Valley Medical Center Laboratory 304-647-6060
Plateau Medical Center Laboratory 304-469-8621

Patient Preparation

Call CAMC LabWorks at 304-388-5070 or 800-445-5278, 24 hours in advance of draw, to schedule test. 

  1. Patient should have consumed a high carbohydrate (at least 150g) diet at least 3 days prior to the test.
  2. The patient should be ambulatory.  Inactivity decreases glucose.
  3. The patient should be fasting overnight for 8-14 hours.
  4. The patient should engage in minimal activity during the test.  Exercise and emotional stress should be avoided.
  5. The patient should not smoke, chew gum or drink during the test. (1-2 small sips of water are acceptable.)
  6. Patient should remain seated during testing.
  7. Certain drugs such as salicylates, diuretics and anticonvulsants may decrease insulin production and should be avoided at least 3 days prior to the test if medically possible.  Also nicotinic acid, b-adrenergic blocking agents and high doses of some hormones will affect results.
  8. The best time to conduct the test is between 7 a.m. and 12 noon. Call and get
    approval from physician to start testing after 9 a.m. if patient insists.  Explain that time of day will have an effect on results.

Specimen Collection Requirements

Plasma/Serum

Fasting specimen should be collected in a dark green lithium heparin tube.

All other collection times collect 1 grey top, mint green or SST tube.

If fasting glucose is <140 mg/dL, patient will be given glucose beverage. Instruct patient to drink whole amount within several minutes.

Note: Indicate corresponding draw times (1 hour, 2 hour, or 3 hour) on request form and collection tubes.

Specimen Rejection

  • Improperly labeled, collected, stored, and transported
  • Quantity not sufficient
  • Hemolyzed 

Specimen Requirements

Plasma- Mint Green, Dark Green Lithium Heparin or Gray Sodium Fluoride 

Serum- SST gold top, red top

Allow SST or red top to completely clot

Spin and physically separate plasma/serum from contact with cells as soon as possible

4 mL of plasma/serum (minimum 2 mL)

Reference Values

Fasting Reference Value: 74-106 mg/dL

 

Critical Value: <60 or > 500 mg/dL

 

For 1 hour, 2 hour and 3 hour glucoses:

No established reference values

The test result must be integrated into the clinical content for interpretation.

 

The following are recommendations from the American College of Obstetricians and Gynecologists (ACOG) and the American Diabetes Association (ADA):

Fasting > 95 mg/dL 

1 Hour > 180 mg/dL

2 Hour > 155 mg/dL

3 hour > 140 mg/dL

Methodology

Photometric hexokinase G-6-PDH

Days Test Set Up and Turnaround

Monday through Friday, Dayshift

AM Collection Expected by 9AM same day
Routine Expected within 24 hrs
Stat Expected within 1 hr
Timed Expected results are test dependant

CPT Coding

82951