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Glucose, Fasting and Gestational-135 Cutoff [1430X]
Test Code143089
CPT Codes
82947, 82950
Preferred Specimen
1 mL timed plasma collected in (x2) fluoride/oxalate (gray-top) tubes
Patient Preparation
Fasting is 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 each specimen
Other Acceptable Specimens
2 full tubes of timed whole blood collected in fluoride oxalate (gray-top) tube • 1 mL (x2) timed plasma collected in: Lithium heparin (green-top) or sodium heparin (green-top) tubes • 1 mL (x2) timed serum collected in: Serum separator tubes (SST®)
Instructions
This test should be performed between weeks 24 and 28 of gestation.
Immediately after a fasting specimen is obtained, have patient ingest a 50 g load of glucose. Draw subsequent specimen 1 hour later. Label each specimen with the specific draw time. Collect 2 - 1 mL plasma specimens from a fluoride/oxalate (gray-top) tubes preferred, and ship plasma tubes at room temperature. Serum specimens are also accepted.
Serum and plasma submissions must be separated from cells.
Whole blood: ship tubes on refrigerant coolant.
Immediately after a fasting specimen is obtained, have patient ingest a 50 g load of glucose. Draw subsequent specimen 1 hour later. Label each specimen with the specific draw time. Collect 2 - 1 mL plasma specimens from a fluoride/oxalate (gray-top) tubes preferred, and ship plasma tubes at room temperature. Serum specimens are also accepted.
Serum and plasma submissions must be separated from cells.
Whole blood: ship tubes on refrigerant coolant.
Transport Temperature
Plasma and serum: Room temperature
Whole blood: Refrigerated (cold packs)
Whole blood: Refrigerated (cold packs)
Specimen Stability
Sodium fluoride plasma
Room temperature: 7 days
Refrigerated: 7 days
Frozen: 28 days
Heparinized plasma
Room temperature: 48 hours
Refrigerated: 7 days
Frozen: 28 days
Serum
Room temperature: 4 days
Refrigerated: 7 days
Frozen: 28 days
Whole blood (gray-top) tube
Room temperature: 24 hours
Refrigerated: 72 hours
Frozen: Unacceptable
Room temperature: 7 days
Refrigerated: 7 days
Frozen: 28 days
Heparinized plasma
Room temperature: 48 hours
Refrigerated: 7 days
Frozen: 28 days
Serum
Room temperature: 4 days
Refrigerated: 7 days
Frozen: 28 days
Whole blood (gray-top) tube
Room temperature: 24 hours
Refrigerated: 72 hours
Frozen: Unacceptable
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Unspun serum or plasma separator tube (SST or PST) • Red-top or green-top tube (serum or heparinized plasma not separated from cells) • Anticoagulants other than lithium heparin, sodium heparin or fluoride/oxalate
Methodology
Spectrophotometry (SP)
Setup Schedule
Set up: Sun a.m., nights; Mon-Fri (all shifts), Sat a.m.; Report available: Next day
Limitations
Glucose levels may be depressed if sample is left on clot for an excessive length of time.
Reference Range
| Glucose, Plasma | 65-99 mg/dL |
| Glucose, Gestational Screen (50g), 135 Cutoff | <135 mg/dL |
Clinical Significance
A value of 135 mg/dL or greater indicates the need for a full diagnostic, gestational glucose tolerance performed in the fasting state to determine if the patient has gestational diabetes.
