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Test Code LABCHOBGTT Glucose Tolerance Test, Plasma

Specimen Type

Blood

Container

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Preferred Volume

3 mL

Offsite Collection Instructions

Refer to Glucose Tolerance testing protocol in the Glucose Tolerance Testing Collection link
 

The patient is to eat no food after midnight prior to the test (fasting 8-14 hours before test).
 

Samples must be labeled with patient name, medical record number and elapsed time since 75 gram glucose beverage ingestion (i.e. 30, 60, 90, 120 minutes).

UCMC Collection Instructions

Refer to Glucose Tolerance testing protocol in the Glucose Tolerance Testing Collection link
 

The patient is to eat no food after midnight prior to the test (fasting 8-14 hours before test).
 

Samples must be labeled with patient name, medical record number and elapsed time since 75 gram glucose beverage ingestion (i.e. 30, 60, 90, 120 minutes).

Availability

Monday-Friday, 7am-7pm

Turnaround Time

3 hours

STAT Availability

Not Available

Test Usage

This test is used primarily to diagnose diabetes mellitus. The test involves measuring venous plasma glucose in samples taken before and at varying intervals after a 75 gram dose of oral glucose given to an adult patient who is fasted 8-14 hours before the test.

Test Methodology

Spectrophotometric, enzymatic endpoint

CPT Code

TOL3: 82951

TOLP: 82952

Minimum Volume

2 mL

Reference Range

In a position statement of the American Diabetes Association (ADA) on the Diagnosis and Classification of Diabetes Mellitus [Ref. 2], criteria for the provisional diagnosis of diabetes mellitus may be made when:

a. Fasting plasma glucose level of  126 mg/dL   OR
b. A 2 hour post load glucose level of  200 mg/dL during an oral glucose tolerance test (using a 75 gram glucose load)   OR
c. Any casual (random) glucose level of  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:
a. Impaired fasting glucose (IFG), where fasting plasma glucose levels are 100-125 mg/dL
b. Impaired glucose tolerance test (IGT), where 2 hour post 75 gram glucose load glucose level are 140-199 mg/dL during an oral glucose tolerance test

 

REFERENCE

1. Classification and diagnosis of diabetes mellitus and other categories of glucose intolerances. Diabetes 28:1039-1057, 1979.

2. Diagnosis and classification of diabetes mellitus. Diabetes Care 2010; 33 (Suppl 1):S63-S69.

Critical Results

Critical value <40 or >500mg/dL

Fee Code

TOL3: 43414

TOLP: 43375

 

Test Includes

quantitative glucose in plasma on fasting (10 hours) specimen and specimens collected 30, 60, 90 and 120 minutes post ingestion of 75 gram glucose load.