Glucose Tolerance Test, Gestational

Test Code

GTTOB

Includes

Fasting, 1-Hour, 2-Hour, 3-Hour glucose

Preferred Specimen

Four - 1 mL plasma specimens collected in fluoride/oxalate (gray-top) tubes

Patient Preparation
Fasting required. Fasting is defined as no consumption of food or beverage other than water for at least 8 hours before testing.

Minimum Volume

0.5 mL for each specimen

Other Acceptable Specimens

Fluoride/oxalate whole blood

Instructions

A fasting specimen is obtained and once it is resulted by lab, have patient ingest a 100 g load of glucose. Draw subsequent specimens 1, 2 and 3 hours later. Label each with the specific draw time.

Transport Container

Fluoride/oxalate (gray-top) tubes

Transport Temperature

Ambient

Specimen Stability

Whole blood (gray-top) tube:
Ambient: 24 hours
Refrigerated: 72 hours

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)

Specimens other than fluoride/oxalate tubes

Methodology
Spectrophotometry (SP)

Setup Schedule

Test may be performed at hospital sites during open hours Mon-Sat. Please allow time for completion of test.

Report Available

Same day

Limitations

Glucose levels may be depressed if sample is left on clot for an excessive length of time.

Reference Range

See report

Clinical Significance

Plasma glucose levels may be abnormally high (hyperglycemia) or abnormally low (hypoglycemia). Glucose measurements are used in the diagnosis and treatment of carbohydrate metabolic disorders.

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.