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GLUCOSE, OB TOLERANCE, 2 HOUR

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

Mnemonic

GTT OB2HR

Includes

Fasting Glucose, 1 and 2 hour glucose levels collected after a 75 gram load of glucola

Guidelines

Recommended by the ADA to be used in pregnant patients at 24-28 weeks gestation for diagnosing Gestational Diabetes. Do not confuse this test with the GLU 2HR. The GLU 2HR is used to diagnose diabetes in non-pregnant patients and pregnant patients during their initial visit.

Specimen Collection Requirements

Patient Preparation

Patient should fast for 8-14 hours before administering test. Collect fasting specimen. Administer 75 gram load of glucola. Collect specimens 1 and 2 hours after consumption of glucola beverage.

Collect

Preferred: Plasma, one 4.0 mL gray (sodium fluoride/potassium oxalate) top tube for each collection. 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 for each collection. DO NOT MIX SPECIMEN TYPES DURING COLLECTION.

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

CPT Codes

82951

Last Updated: Wednesday, May 24, 2017 11:43:48 AM


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