Test
Name

Glucose Tolerance Test, 100 g
load

Test Code

2032

Unit

mg/dL

Station

Chemistry

Synonym Name/Abbreviation

Postprandial Sugar, PP Glucose, Glucose tolerance 3 h

CPT Code

82951, 82952

Performing Facility

American Medical Labs, Herzliya
Pituah

Analyzer

Roche cobas 6000

Test Method

 Enzymatic
colorimetric assay

AML Preferred Tube

5 mL SST gel (separate serum within 45 minutes). Alternate
tube: NA-Fl (grey top tube)

Storage Instructions

Refrigerated.

 Separate serum from cells within 45 minutes.
Stability:

 8 hours at 15‑25 �C, 72 hours at 2 to 8�C
Gray top tube whole blood is stable 24 hours.

Min. Volume

1 mL

Comments

It is not the optimal test for diagnosis of types 1 and 2
diabetes mellitus. American Diabetes Association (ADA) recommends the
plasma fasting glucose rather than the OGTT for the diagnosis of type 1
& 2 diabetes mellitus.

Turn-Around-Time

One day.

Intended Use

This
is the recommended study for diagnosis of gestational diabetes in pregnant
patients. It is used to predict perinatal morbidity, risk of fetal
abnormality and perinatal mortality.

Limitations

Poor reproducibility, patient inconvenience, propensity for
overdiagnosis of diabetes melllitus. Impaired test result in not
equivalent to diabetes mellitus.

Patient Preparation

This test should be done in the morning after an overnight
fast of between 8 and 14 hours, and after at least 3 days of unrestricted
diet (150 or more grams carbohydrate per day) and unlimited physical
activity. The patient should remain seated and should not smoke throughout
the test. Patient can have nothing by mouth except water during test
period. GLUCOSE DOSE: 100 grams.

Specimen
collection:
Draw fasting specimen just prior to 100 gram glucose load. Draw 1 hour, 2
hour and 3 hour post-dose specimens.

Reasons for Rejection

Gel tubes received unspun; improper specimen labeling;
nonfasting patient

 Pregnant
Reference Ranges

 Two or more of
the following threshold
values must be met or exceeded to confirm gestational
diabetes:

Fasting 95
mg/dL

1 hour 180
mg/dL

2 h 155 mg/dL

 3 h 140  mg/dL

 These
criteria apply to the 3-hour
(100 gram) ADA glucose tolerance testing  protocol for gestational
diabetes.