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HelpTest Code LAB49 Glucose Tolerance Test, 2 Hour, Plasma or Serum
Additional Codes
| Test Name in EPIC | EPIC Test Code | Mnemonic |
|---|---|---|
| GLUCOSE TOLERANCE, 2HR | LAB49 | GTT2H |
Useful For/Utility
Diagnosing and managing diabetes mellitus and other carbohydrate metabolism disorders including gestational diabetes, neonatal hypoglycemia, idiopathic hypoglycemia, and pancreatic islet cell carcinoma
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. A 10 to 16 hour fast is required.
2. Patient should be instructed to refrain from smoking just before and during test.
Performance of Test
1. Draw a PST green top (lithium heparin) tube specimen from a fasting patient.
2. Deliver sample to lab promptly.
3. Patient is given glucose drink as follows:
a. 1.75 g/kg of body weight for patients <88 lbs
b. 75 g for patients >88 lbs
4. Draw blood specimens exactly 2-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, 2-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, 2-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
Fasting: 70-99 mg/dL
2 hour: See report