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Test Code GTT3G GLUCOSE TOLERANCE 3 HOUR, GEST

Important Note

  1. Patients are required to have an appointment for Glucose Tolerance Testing and should contact the Outpatient Laboratory Services site, 752-1737 to schedule an appointment.
  2. Medical Offices should provide patients with the Patient Information Sheet for Glucose Tolerance Testing.
  3. Medical Office Clinical Staff members should review the Medical Practice Protocol for patient GTT.
  4. Offices should contact the Laboratory for drawing instructions if specimens are to be drawn at the Physician’s Office.

Methodology

Colorimetric

 

Useful for diagnosing glucose intolerance in pregnant women at high-risk for gestational diabetes and for confirmation of abnormal GLU.CHAL “Glucose Challenge, Plasma or Serum” when performed at 24 to 28 weeks of pregnancy.

Specimen Requirements

Patient Preparation:

  • Patient must be on a normal diet for 3 days prior to testing
  •  Fasting for at least 8 to 14 hours prior to test

 

Procedure:

See “Glucose Tolerance Testing, Gestational” in Special Instructions for dosage and collection times. 

 

Specimen Collection:

Submit only 1 of the following specimens for each draw time:

 

Preferred:

Plasma

Container/Tube: Green-top (lithium heparin) tube(s) or grey-top (potassium oxalate/sodium fluoride) tube(s)

Specimen Volume: 1 mL (minimum volume: 0.5 mL) of plasma-Grossly hemolyzed specimen is not acceptable.

Collection Instructions: Spin down within 1 hour of draw.

Note:

  1. Grey-top tube is stable for 24 hours after drawing specimen.
  2. Label specimens appropriately (time of draw and as plasma).

 

Alternate:

Serum

Serum Gel Tube

Container/Tube: Serum gel tube(s)
Specimen Volume: 1 mL (minimum volume: 0.5 mL) of serum-Grossly hemolyzed specimen is not acceptable.

Collection Instructions: Spin down within 1 hour of draw.

Note: Label specimens appropriately (time of draw and as serum).

 

Alternate:

Serum

Plain, Red-Top Tube

Container/Tube: Plain, red-top tube(s)
Specimen Volume: 1 mL (minimum volume: 0.5 mL) of serum-Grossly hemolyzed specimen is not acceptable.

Collection Instructions: Spin down within 1 hour of draw.

Note: Label specimens appropriately (time of draw and as serum).

Day(s) Test Set Up

Monday through Sunday

Reference Values

Fasting: <95 mg/dL

1 hour: <180 mg/dL

2 hour: <155 mg/dL

3 hour: <140 mg/dL

 

Diagnosis of gestational diabetes requires that 2 or more of the above limits are met or exceeded.

 

Critical values (automatic call-back): <50 mg/dL or >500 mg/dL

Performing Laboratory

Logan Health Medical Center-Chemistry

Test Classification and CPT Coding

82951-Glucose tolerance test, 3 specimens

82952-One additional specimen (if appropriate)

Specimen Transport Temperature

Refrigerate

Special Instructions