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HelpTest Code XGTT Glucose tolerance, 2 hours
Additional Codes
| Hospital Ordering Code |
|---|
| LAB??? 2 hour Adult Diabetic Tolerance |
Specimen Requirements
Submit only 1 of the following specimens:
Specimen Type: Plasma
Container/Tube: Grey top (potassium oxalate/sodium fluoride)
Specimen Volume: 0.5 mL
Additional Information: Label specimen appropriately (plasma).
Specimen Type: Serum
Container/Tube: Serum gel
Specimen Volume: 0.5 mL
Additional Information: Label specimen appropriately (serum).
Performing Laboratory
Unity Point-Sioux City-Chemistry
CPT
82951
82952 x2
Methodology
Enzymatic with Hexokinase
Specimen Requirements Additional Information
Patient preparation is very important.
1. The patient should be placed on an unrestricted diet containing 1.75 g of carbohydrate per kg body weight for three days prior to the test. If carbohydrate intake has been too low preceding the test, a false diabetic curve may be obtained. If possible, medications known to cause glucose intolerance should be discontinued.
2. The patient must fast for 10 - 16 hours before testing. The patient should be ambulatory (bed-rest causes impaired glucose tolerance.
3. The patient is allowed to drink water during the fast. No other food or beverage is allowed. The patient is also not allowed to smoke or chew gum because these activities stimulate the digestive process and may affect test results.
4. A fasting sample is obtained.
5. Give the patient a standard 75 gm glucose solution. The entire solution should be consumed within 5 minutes. If the patient vomits during the procedure, the ordering physician should be consulted to determine if the test should be continued.
6. Ask the patient to remain quiet for the duration of the test.
7. Start timing the procedure when the patient finishes drinking the glucose solution.
8. Obtain blood samples at ½ hour, 1 hour, 1 ½ hour, and 2 hours. Specimens should be labeled with both the exact time of collection and the time interval of the test, e.g., ½ hr, 1 hr, etc.
9. The patient will remain in the lab until the final glucose level is obtained from Chemistry. If the result is below 70, the patient must be given something to eat prior to discharge.
10. No food, alcohol, smoking or chewing gum is allowed throughout the test period. Water intake is allowed.
Specimen Transport Temperature
Ambient
Day(s) Test Set Up
Monday through Sunday
Expected Values
1. Criteria for Diabetes Mellitus in non-pregnant adults should be restricted to the following:
a) A random glucose level of 200 mg/dL or greater, plus classic signs and symptoms including polyuria, polydipsia, ketonuria, and rapid weight loss.
b) A fasting glucose of 140 mg/dL or greater on at least two occasions.
c) A fasting glucose level of less than 140 mg/dL plus a two hour level of 200 mg/dL or greater and at least one other level between 0 and 2 hours of 200 mg/dL or greater, confirmed by repetition.
2. In normal patients, blood glucose levels peak within 30 minutes to 1 hour after glucose ingestion. The peak in glucose levels triggers the release of insulin, which brings glucose levels back down to fasting levels within about 2 hours. Because diabetics have an inadequate or absent insulin response, glucose levels peak at higher levels and are slower to return to fasting levels. If blood is not drawn on time, it is important for the phlebotomist to note the discrepancy so that the physician will take this into consideration.