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Test Code GTT P2H Glucose Tolerance 2 Hr

Important Note

When administered by Seattle Children's lab, this test must be scheduled with the Chemistry Laboratory 206 987-3860.  Outside orders should be faxed to 206 985-3124.

 

If administering in Infusion Clinic, order in EPIC and send samples to main campus for testing.

GTT can be performed at Bellevue or South infusion with glucose testing run in the lab.  Glucose administration is performed by infusion team.

Clinical System Name

Glucose Tolerance 2 Hr - 2 Tests

Synonyms

Modified OGTT

Sample Requirements

Specimen: Whole Blood

Container(s): Lt. Green/Lithium Heparin Microtainer, Dark Green/Sodium Heparin,

Preferred Vol: 1 mL

Minimum Vol: 0.5 mL 

Notes:  Call Chemistry when patient arrives for appointment (7-3860). Use microtainer collection for fastest turnaround time. 

 

 

Processing Instructions

Reject due to: Age of specimen, hemolysis, line contamination

Spin: Y

Aliquot: Y

Temp: 2-8oC

Storage location: Fasting glucose performed by chemistry tech on EPOC. Deliver 2 hr sample to Core.

Off-site collection: Bellevue and South: Avoid hemolysis and line contamination. Spin blood, refrigerate serum or plasma. Method not affected by sodium fluoride. Serum or plasma must be removed from red blood cells within 30 minutes for accurate glucose levels.

All other sites: Call Chemistry Laboratory to schedule test (206) 987-3860.  Test must be collected at Seattle Children's.

Stability

 

Specimen Type Temperature Time
whole blood RT 30 m
Plasma RT

≤ 24 H
Plasma 2-8oC

≤ 7 D
Plasma -20oC or -70oC

≤ 365 D

Note:  metabolism of glucose by the cells is approximately 7% per hour at room temp. 

Availability

STAT Performed TAT
N M - F, day shift 1 d

 

Performing Laboratory

Seattle Children's Laboratory    

Department

Department:  Chemistry

Location: Chem East

Phone Number: 206-987-3860

 

CPT Codes

82947

82950

Methodology

Method: Amperometric by epoc (fasting sample) Colorimetric method by Vitros 4600 or Rapidpoint 405 (2 H sample)

Analytical Volume:     Epoc 0.1 mL whole blood

                                     Vitros 4600: 0.02 mL + 0.03 mL dead space

                                     Rapidpoint 405: 0.20 mL

Limitations: Method is affected by line contamination and hemolysis. Not affected by sodium fluoride.

 

Reference Range

 

FASTING GLUCOSE (mg/dL)   2 HOUR POST GLUCOSE (mg/dL)  
< 110  Normal < 140  Normal
≥ 110  and < 126 Impaired ≥ 140 and < 200  Impaired
≥ 126  Diabetes ≥ 200  Diabetes

 

Description

Call Chemistry Laboratory to schedule the test (206) 987-3860 at main campus.  Test includes STAT fasting glucose and a glucose 2 hr post Glucose load.  Glucose drink is given to the patient only after fasting glucose result is completed by Chemistry technologist.  If fasting result is <126 mg/dL, Chemistry technologist will administer glucose drink.