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Test Code LAB1760 Glucose Tolerance Test, 75 G 2 Hour Gestational 1 Step Diagnostic Screen, 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 1-hour post consumption.

4. 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 gram 2 hour gestational 1 step diagnostic: 
The one-step OGTT is performed using a 75-gram oral challenge after fasting in women between 24-28 weeks gestation. The fast should be at least 8 hours. A diagnosis of gestational diabetes is made when any of the following plasma glucose measurements are met or exceeded: 
Fasting: 92 mg/dL
1h: 180 mg/dL
2h: 153 mg/dL

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

Literature Reference:

Classification and Diagnosis of Diabetes: Standards of Medical Care in Diabetes -2022. Diabetes Care;45(supplement_1):S17-S38.

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
Fasting Glucose 1552-9
Glucose 1 hour post 75 g glucose 1507-.
Glucose- 2 hours post 75 g glucose PO 1518-0