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HelpTest Code LAB48 Glucose Tolerance Test, Obstetric 3 Hour, Plasma or Serum
Additional Codes
| Test Name in EPIC | EPIC Test Code | Mnemonic |
|---|---|---|
| GLUCOSE TOLERANCE, 3HR OB | LAB48 | GTT3H |
Useful For/Utility
Diagnosing and managing gestational diabetes.
Methodology
Hexokinase/G-6-PDH
Clinical Information
The most common disease related to carbohydrate metabolism is diabetes mellitus, which is characterized by insufficient blood levels of active insulin. Symptoms include polyuria, abnormally elevated blood and urine glucose values, excessive thirst, constant hunger, sudden weight loss, and possibly elevated blood and urine ketones. Patients with "impaired" glucose regulation have a markedly increased risk of developing type 2 diabetes and should be counseled for lifestyle changes and followed up with more testing. Indications for screening and testing include strong family history, marked obesity, history of babies over 9 pounds, and recurrent skin and genitourinary infections.
(Chapter 25: In Tietz Textbook of Clinical Chemistry. Fourth edition. Edited by CA Burtis, ER Ashwood, DE Bruns. WB Saunders Company, Philadelphia, 2006, pp 837-907)
Specimen Requirements
Patient Preparation
1. If doctor specifies, patient should consume 300 g of carbohydrates each day for 3 days prior to testing.
2. A 10 to 16 hour fast required.
3. Patient should be instructed to refrain from smoking just before and during test.
4. Provide patient with the Glucose Tolerance Test (G.T.T.) Patient Brochure available from the laboratory. (See Glucose Tolerance Test [G.T.T.] Patient Brochure in Special Instructions.)
Performance of Test
1. Draw a PST green top (lithium heparin) tube from a fasting patient.
2. Deliver specimen to laboratory promptly.
3. Patient is given 100 g (300ml) glucose drink.
4. Draw blood specimens exactly 1-, 2-, and 3-hours post Glucola ingestion.
Specimen Collection
Submit only 1 of the following specimens:
Preferred:
Specimen Type: Plasma
Container/Tube: Light-green top (lithium heparin gel)
Specimen Volume: 1 mL
Specimen Minimum Volume: 0.5 mL
Collection Instructions:
1. Separate plasma from cells within 2 hours of draw.
2. If plunger filters are used, immediate removal of plasma is indicated unless an air gap can be created between the device and specimen.
Additional Information: Label specimens appropriately (fasting, 1-, 2-, 3-hour, and as plasma).
Alternate:
Specimen Type: Serum
Container/Tube: Serum gel
Specimen Volume: 1 mL
Specimen Minimum Volume: 0.5 mL
Collection Instructions:
1. Separate serum from cells within 2 hours of draw.
2. If plunger filters are used, immediate removal of serum is indicated unless an air gap can be created between the device and specimen.
Additional Information: Label specimens appropriately (fasting, 1-, 2-, 3-hour, and as serum).
Specimen Transport Temperature
Refrigerate 5 days/Ambient 8 hours OK/Frozen OK
Day(s) Test Set Up
Monday through Sunday
Performing Laboratory
Chemistry-
St. Joseph's - Baxter Clinic Lab, St. Joseph's - Brainerd Clinic Lab, St. Joseph's Medical Center Lab
Ashland Clinic Lab, Chisholm Clinic Lab, Deer River Hospital Lab, Ely Clinic Lab, Hayward Clinic Lab, Hibbing Clinic Lab, International Falls Clinic Lab, Moose Lake Hospital Lab, Northern Pines Lab, Sandstone Hospital Lab, SMDC Clinical Lab, Spooner Clinic Lab, St. Mary's Hospital - Superior Lab, Virginia Hospital Lab
Ada Hospital Lab, Fargo Hospital Lab, Fosston Hospital Lab, Holy Trinity Hospital Lab, South University Clinic Lab, St. Mary's - Detroit Lakes Hospital Lab
Test Classification and CPT Coding
82947
Reference Values
Reference Ranges
GTT 3 Hour OB Glucose Tolearance Test
Dose: 100 gram Oral Glucose Load
Fasting: <95 mg/dL
1 Hour: <180 mg/dL
2 Hour: <155 mg/dL
3 Hour: <140 mg/dL