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Glucose Tolerance Test, Miscellaneous

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

Mnemonic

GTT MISC

Synonym

Miscellaneous non-OB Oral Glucose Tolerance Test - 3, 4 or 5-hour Non-OB Oral Glucose Tolerance Test - Glucose Tolerance Time Specified - OGTT - GTT

Includes

Test includes 1 or more of the following: Fasting Glucose and/or 0.5, 1, 1.5, 2, 3, 4 and 5 hour glucose levels collected after administration of glucose load. Fasting specimen is required for 75gram and 100gram glucose load. Physician should indicate which specimens are to be collected on the requisition.

Guidelines

Acceptable glucose loads include: 50 g, 75 g, or 100 g of glucola beverage or a meal.  Indicate on the requisition which one should be used.

Specimen Collection Requirements

Patient Preparation

Patient should fast for 8-14 hours before administering test (if requested). Collect fasting glucose specimen (if requested). Administer specified glucose load. Collect timed specimens after consumption of the glucola beverage or meal.

Collect

Preferred: plasma, 4.0 mL gray (sodium fluoride/potassium oxalate) top tube, for each collection. Also acceptable: serum or plasma, 5.0 mL gold (SST), 7.0 mL red or 3.0 mL mint green (lithium heparin, PST) top tube. DO NOT MIX SPECIMEN TYPES.

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. Gray top tubes must be spun, and plasma separated from cells within 24 hours.

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

UNSPUN (WHOLE BLOOD): Refer to Handling section above.

 

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

Not established.

Comments

ADA guidelines do not recommend using this test. For non-pregnant patients, recommend using the Glucose, Challenge Test, 2 hour. For pregnant patients, recommend using the Glucose, OB, Tolerance, 2 hour.

CPT Codes

82951

Last Updated: Sunday, August 16, 2020 05:18:04 PM


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