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HelpTest Code LAB5017 Glucose Tolerance Test (GTT), Gestational, 3 Hour Post Dose
Performing Laboratory
Asante Rogue Regional Medical Center / Asante Three Rivers Medical Center
Specimen Minimum Volume
0.5 mL
Billing Code
2050698, 2050722
Methodology
Oxygen Rate Electrode
Specimen Requirements
Sodium Fl (NaF) Gray top tube preferred
Lithium Heparin Green top tube (must be centrifuged within 1-2 hrs, preferably within 1 hr)
Outpatient clients;
Collection:
1. Collect fasting specimen
2. Administer dextrose
3. Post dextrose collect: 1 hour, 2 hour, and 3 hour specimens
Patient should be fasting 12 hours prior to test.
Patient should have had adequate food intake with at least adequate carbohydrates for 3 days prior to test.
NO CAFFEINE, NICOTINE OR EMOTIONAL STRESS until all specimens have been collected.
Avoid drugs which:
1. Increase blood sugar: birth
control pills, salicylates, diuretics, alcohol, steroids, etc.
2. Decrease blood sugar:
insulin (omit A.M. dose at least), sulfonylureas (omit for 3 days),
propranolol (omit for 24 hours).
Activities:
Generally patient should be seated, but minimal walking is
permitted.
Dosage:
100 gm dextrose after normal fasting
glucose result.
The physician will be contacted and consulted prior to proceeding with tolerance if fasting glucose is above a specific value.
Note: Other chemistry tests cannot be analyzed using the Gray NaF tube.
Day(s) Test Set Up
Monday through Sunday
Test Classification and CPT Coding
82951 Glucose; tolerance test (GTT), 3 specimens (includes glucose)
82952 Glucose; tolerance test, each additional beyond 3 specimens
Additional Information
Use: The Glucose Tolerance Test only establishes the presence of
glucose intolerance. It is used in patients with borderline
fasting and postprandial glucose to support or rule out the
diagnosis of diabetes mellitus. Some use it in unexplained
neuropathy, hypertriglyceridemia, impotence, diabetes-like renal
diseases, retinopathy, re-evaluation of prior diagnosis made under
substandard conditions and with necrobiosis lipoidica
diabeticorum. The GTT is used to work up glycosuria without
hyperglycemia. Predict perinatal morbidity in pregnancy,
diagnose gestational diabetes. Glucose intolerance is due to
obesity in some subjects.
Abnormal curves may relate to Cushing’s syndrome,
pheochromocytoma or acromegaly. The Gestation GT is used
specifically by obstetric physicians to minimize trauma and
unnecessary testing in a pregnant woman.
Specimen Transport Temperature and Stability
Centrifuge SST collection tube within 1 hour of collection (no
longer than 2 hours).
Stable 8 hours at room temperature, 24 hours refrigerated at
2°- 8°C on separated SST.
If centrifuge not available, the sample must be drawn in a gray
sodium fluoride (NaF) tube.
Performing Department
Chemistry