Glucose Tolerance Test, 3 Specimens (75g)

Test Code

23475

CPT Codes
82951

Includes

Fasting, 1-Hour, 2-Hour glucose

Preferred Specimen

1 mL plasma collected in each of three separate 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 (x3)

Other Acceptable Specimens

Plasma collected in each of three separate fluoride/oxalate (gray-top) tubes in a plastic screw-cap vial • Serum (separated from cells immediately) collected in each of three separate plastic screw-cap vials • Spun serum collected in each of three separate serum separator tubes • Plasma collected in each of three separate lithium heparin (green-top) tubes in a plastic screw-cap vial • Plasma collected in each of three separate sodium heparin (green-top) tubes in a plastic screw-cap vial • Whole blood collected in each three separate sodium fluoride/oxalate (gray-top) tubes

Instructions

Immediately after a fasting specimen is obtained, have patient ingest a 75 g loaded dose of glucose. Draw subsequent specimens 1 and 2 hours later. Label each with the specific draw time.

Note: Serum and plasma submissions must be separated from cells.

Transport Temperature

Sodium fluoride plasma (preferred) and serum: Room temperature
Heparinized Plasma and whole blood: Refrigerated (cold packs)

Specimen Stability

Sodium fluoride plasma (preferred)
Room temperature: 7 days
Refrigerated: 7 days
Frozen: 28 days

Whole blood
Room temperature: 24 hours
Refrigerated: 72 hours
Frozen: Unacceptable

Serum
Room temperature: 4 days
Refrigerated: 7 days
Frozen: 28 days

Heparinized plasma
Room temperature: 48 hours
Refrigerated: 7 days
Frozen: 28 days

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

Unspun SST • Red-top or non-plasma separator (PST) green-top tubes • Anticoagulants other than lithium heparin, sodium heparin or fluoride/oxalate

Methodology
Spectrophotometry (SP)

Setup Schedule

Set up: Daily; Report available: Next day

Limitations

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

Reference Range

American Diabetes Association Diagnostic Criteria for Diabetes Mellitus
Glucose Value (mg/dL)
Interpretation	Fasting	1-Hr Tolerance	2- Hr Tolerance
Normal	<100	Not established	<140
Impaired Fasting	100-125
Impaired Tolerance			140-199
Diabetes	≥126*		≥200*
*Must be confirmed by testing on a subsequent day.

Clinical Significance

This test is used for the routine diagnosis of diabetes in children and the non-pregnant adult. For pregnant females see test "Glucose Tolerance Test, Gestational, 4 Specimens (100 g)". For appropriate interpretation of this test, the patient must fast overnight and ingest a 75 g load of glucose. Immediately after, a fasting specimen is obtained. For children, the glucose load is 1.75 g/Kg of body weight, up to 75. The diagnosis of diabetes is made if the fasting glucose is ≥126 mg/dL or if the 2-hour specimen is ≥200 mg/dL.

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.