A B C D E F G H I J K L M N O P Q R S T U V W X Y Z # |
Glucose Tolerance Test, 3 Specimens (75g)
Test Code23475
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.
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)
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
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.
Performing Laboratory
Quest Diagnostics Nichols Institute
14225 Newbrook Drive
Chantilly, VA 20153