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Test Code LAB5016 Glucose Tolerance Test (GTT), Gestational, 2 Hour Post Dose
Performing Laboratory
Asante Rogue Regional Medical Center / Asante Three Rivers Medical Center
Billing Code
2050698, 2050722
Methodology
Oxygen Rate Electrode
Specimen Requirements
Yellow (Gold) top tube (SST) - preferred
Lithium Heparin Green top tube (must be centrifuged within 1-2 hrs, preferably within 1 hr)
Outpatient clients must draw SST.
Limited 2 hour stability with PST.
Gray-top (Sodium Fluoride) tube is indicated for those clients that
do not have access to a centrifuge.
1 full SST or green-top PST (heparinized), for each sample
collected (use same sample type for all samples).
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.
GTT WILL NOT BE PERFORMED IN CONJUNCTION WITH OTHER CLINICAL
PROCEDURES.
Dosage:
75 gm dextrose after normal fasting glucose result. The
physician will be contacted prior to proceeding with tolerance if
fasting glucose is greater than 140 mg/dL.
Collection:
Fasting Plasma Glucose
1 Hour Plasma Glucose
2 Hour Plasma Glucose
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 collection tube and refrigerate within 2 hours of collection. Primary tube: Spun SST stable 24 hours at 2° to 8° C. Serum stable 48 hours if aliquoted and refrigerated at 2° to 8° C.
Performing Department
Chemistry