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GLUCOSE, CHALLENGE TEST, 2 HOUR

For patient preparation instructions, refer to Glucose Tolerance Tests-Patient Preparation Instructions.

Mnemonic

2HR GLU

Synonym

2 Hour Non-OB Oral Glucose Tolerance Test - OGTT - GTT

Includes

Fasting Glucose and 2 hour glucose post 75 gram load glucola

Guidelines

Recommended by the ADA to be used in non-pregnant & pregnant patients. Do not confuse this test with the GTT OB 2HR. See Comments for more information.

Specimen Collection Requirements

Patient Preparation

Patient should fast for 8-14 hours before administering test. Collect fasting glucose specimen. Administer 75 gram load of glucola beverage. Collect specimen 2 hours after consumption of glucola beverage.

Collect

Preferred: Plasma, one 4.0 mL gray (sodium fluoride/potassium oxalate) top tube, also acceptable: Serum or Plasma, one 5.0 mL gold (SST), 7.0 mL red or 3.0 mL mint green (lithium heparin, PST) top tube

Handling

The gold, red and green top tubes must be delivered to the lab immediately. Allow serum to clot completely at room temperature (minimum: SST - 30 minutes and red top tubes - 60 minutes). Preferably, separate serum or plasma from cells within 1 hour of collection. If unable to spin, preferred specimen is gray (sodium fluoride/potassium oxalate) top tube.

Preferred Volume

1.0 mL Serum/Plasma per specimen

Minimum Volume

0.25 mL Serum/Plasma (0.60 mL minimum whole blood draw) per specimen

Transport

Refrigerated (2-8°C)

Rejection Criteria

Grossly hemolyzed specimens, timed specimens collected outside the ±10 minute window

Stability

AFTER SEPARATION FROM CELLS:

SODIUM FLUORIDE/POTASSIUM OXALATE PLASMA: Room Temperature (18-26°C): 24 hours; Refrigerated (2-8°C): 7 days; Frozen (≤ -20°C): 1 month

SERUM OR LITHIUM HEPARIN PLASMA: Room Temperature (18-26°C): 8 hours; Refrigerated (2-8°C): 3 days; Frozen (≤ -20°C): 1 month

Testing Information

Performed

Schedule testing with one of the approved Legacy Facilities. Please refer to Glucose Tolerance Tests-Patient Preparation Instructions.

Reported

24 hours

Method

UV spectrophotometry

Reference Values

Reference Values

Comments

For pregnant patients, this test should only be used for diagnosing overt diabetes during the initial prenatal visit. GTT OB 2HR should be used for diagnosing Gestational Diabetes at 24-28 weeks gestation.

CPT Codes

Fasting: 82947, 2-hour: 82950

Last Updated: Wednesday, May 24, 2017 11:43:46 AM


Client Services: 503-413-1234