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The University of Chicago Medicine Laboratories

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Mayo Clinic Laboratories

Test Code PPGN Two Hour Post-Prandial Glucose Screen 

Specimen and Container/Tube

Specimen Type: Plasma

Preferred Specimen: Grey Top, NaF/K-Oxalate

Other Acceptable specimens: None

Volume

Preferred Volume: 0.5 mL

Minimum Volume: 0.2 mL

Specimen Stability

Storage Temperature

Stability

Room temperature

3 days

Refrigerated

3 days

Frozen

Not acceptable 

Collection Instructions

  • Collect specimen per standard laboratory collection procedures. 
  • Fasting Draw: a fasting glucose sample is collected from the patient in a grey top (fluoride) vacutainer tube prior to Glucocrush® 75 ingestion. The sample is labeled PPG-Fasting.

 

  • Glucose Beverage Ingestion: 
    • Patient drinks the entire bottle of refrigerator-temperature Glucocrush® 75 within 5 minutes. Timing begins the moment the patient starts drinking.
    • In the case of regurgitation, the test is discontinued unless the ordering physician can be contacted and decides to have the test continued. In this case, a note should be made on the requisition that the test has been performed in spite of the patient’s regurgitation, per doctor’s instruction.
    • No smoking, gum-chewing, or eating during test. The patient may drink small volumes of water. The patient should remain seated as much of the time as possible.
    • In some cases, the ordering physician will ask the patient to have a fasting sample drawn and then to ingest a specified meal and return for the 2-hour sample collection.

 

  • Specimen Collection 
    • A non-fasting sample is drawn into a grey Vacutainer tube 2 hours after finishing Glucocrush® ingestion. Sample is labeled PPG-NONFASTING, with indication of collection time.
    • All blood samples are brought immediately to the lab for testing.

Specimen Handling and Transport Instructions

UCMC Onsite Instructions: 

  • Collect specimen per standard laboratory collection procedures. 

 

UCMC Offsite and UC MedLab Outreach Instructions: 

  • Collect specimen per standard laboratory collection procedures. 
  • Centrifuge specimens at >2500 x g for 10 minutes at room temperature within 2 hours of collection.
  • Aliquot removed plasma into a plastic tubes containing a minimum of 0.2 mL of specimen.
  • Plasma samples must then be sent room temperature at 20 - 25oC

 

Rejection Criteria

  • Common specimen rejected situations include: incorrect specimen type, insufficient volume, missing or incomplete specimen identifiers, incorrect specimen transport, or specimens outside stability limits. 
  • Specimens that are clotted or grossly hemolyzed.
  • Specimens that were transported unspun/whole blood and draw time is greater than 6 hours

Reference Values

 

Test

Age

Sex

Reference Range

Two hour post-prandial fasting glucose

All

All

< 100 mg/dL

Two hour post-prandial 2 hour glucose

All

All

< 140 mg/dL

Critical Values

Analyte

Unit

Low

High

Age

Glucose

mg/dL

<40

>500

>14 days

Turnaround Time

Turnaround times are relative to the time the specimen is received in the test laboratory. 

 

STAT Turnaround Time: Not Available as STAT test

Routine Turnaround Time: 4 hours

Testing Schedule:  24/7

Clinical Indications

This is a screening test for possible diabetes mellitus. The test is so names because it was long ago common screening for diabetes mellitus by measuring blood glucose two hours following a meal. The test involves measuring plasma glucose from a sample taken before and two hours after a 75 gram oral dose of glucose. Alternatively, some physicians prescribe a specified meal in place of the oral glucose. 

Test Components

Two hour post-prandial fasting glucose, two hour post-prandial two hour glucose 

Methodology

Enzymatic Method with hexokinase (Roche Diagnostics)

CPT Codes

82947

LOINC Codes

TBD

Synonyms/Keyword Search

PPGN 

Additional Information

  • Results should always be assessed in conjunction with patient's medical history, clinical examination and other findings.
  • Interpretation of Results: 
    1.  
  • In a position statement of the American Diabetes Association (ADA) on the Diagnosis and Classification of Diabetes Mellitus in 2010 [Ref. 2], criteria for the provisional diagnosis of diabetes mellitus may be made when:
    • Fasting plasma glucose level of ≥ 126 mg/dL  OR
    • A 2 hour post load glucose level of ≥ 200 mg/dL during an oral glucose tolerance test (using a 75 g glucose load)  OR
    • Any casual (random) glucose level or ≥200 mg/dL with symptoms of hyperglycemia or hyperglycemic crisis.
  • Intermediate states indicative of impaired glucose homeostasis that do not meet the diagnostic criteria for diabetes mellitus include:
    • Impaired fasting glucose (IFG), where fasting plasma glucose levels are 100-125 mg/dL
    • Impaired glucose tolerance test (IGT), where 2 hour post 75 g glucose load glucose levels are 140-100 mg/dL during an oral glucose tolerance test.

Last Review Date

6/4/2025