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Test Code LAB5716 Glucose Tolerance Test, 75 G/2 Hour (Type 1/Type 2 Diabetes), Non-Gestational, Plasma

Performing Laboratory

Barnes-Jewish Hospital Laboratory

Methodology

Enzymatic (Hexokinase)

Literature References:

Package insert: Glucose/HK, Roche Corporation, 06/2018.

Specimen Requirements

Patient Preparation:
An 8 to 14 hour fast after 3 days of adequate carbohydrate loading (>150 g/day) is required.

 

Collection Procedure:


1. Draw fasting venous specimen.
2. Give patient 75 g glucose tolerance beverage.
3. Draw venous specimen at 2-hours post consumption.

 

Specimen Type: Plasma

Container/Tube: Grey top (potassium oxalate/sodium fluoride)

Specimen Volume: Full tube

 

Additional Information: Draw times are required.

Day(s) Test Set Up

Monday through Sunday
Turnaround Time:
STAT: 1 hour after receipt in laboratory
Routine: 2 to 4 hours after receipt in laboratory

Test Classification and CPT Coding

82947-Glucose, quantitation

82950-Glucose, post glucose dose

Reference Values

75 G/2 Hour (Type 1/Type 2 Diabetes)

Type 1/Type 2 Diabetes Non-Gestational Adults:
FASTING
Normal: 70-99 mg/dL
Impaired Glucose Tolerance: 100-125 mg/dL
Possible Diabetes: >125 mg/dL
2-HOUR
Normal: 70-139 mg/dL
Impaired Glucose Tolerance: 140-199 mg/dL
Possible Diabetes: >199 mg/dL
Intermediate 2-hour value indicates impaired glucose tolerance, 
while intermediate fasting value indicates impaired fasting glucose.

Critical result (automatic call-back): ≤54 mg/dL or ≥450 mg/dL

Literature Reference:

Diabetes Care 2020;43:Supplement 1,S14-31.

Specimen Transport Temperature

Ambient

Additional Information

For BJH Laboratory Use Only
Alternate Tube:

1 dark green-top (lithium heparin) tube

1 lavender-top (EDTA) tube

1 mint green-top (lithium heparin) tube

1 red-top tube

Laboratory Processing Instructions:

Test performed in BJH Core Lab.  Processed by automated line for delivery to the Cobas 8000. Completed specimens are stored refrigerated for 5 days. 

Test performed in South County Siteman and Ambulatory Cancer Building Lab.  Centrifuge sample and deliver to the Cobas.  Completed specimens are stored refrigerated for 5 days. 

Special Instructions

See Analyte Stability Chart under General Information for a complete list.

LOINC Code Information

 

Name LOINC Code
Glucose in blood 2339-0
Fasting Glucose 1558-6
Glucose- 2 hours post 75 g glucose PO 1518-0