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Test Code LABCHOBGTT Gluocose Tolerance Test, Plasma

Specimen and Container/Tube

Plasma

Rejection Criteria

N/A

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.

Specimen Type

Plasma

Preferred Volume

0.5mL

Offsite Collection Instructions

To be followed in order as listed below.
1. Patient Fasting: The patient is to eat no food after
midnight
prior to the test (fasting 8-14 hours before test).
2. Fasting Draw: A fasting blood sample should be drawn into a
gray
top Vacutainer tube before Glucocrush® 75 ingestion. Sample
is
labeled Fasting or GTT-FAST.
3. Glucose Beverage Ingestion:
a. Patient drinks the entire bottle of refrigerator-temperature
Glucocrush? 75 solution from a paper cup within 5 minutes. The
patient may pour the Glucocrush? 75 over ice if so desired
b. Timing begins the moment the patient starts drinking.
4. Patient Instructions:
a. A copy of the time schedule will be provided to the patient
and
any differences in collection times will be noted on the
specimen’s label.
b. If patient feels ill, or regurgitates solution, the ordering
physician will be notified immediately. In the case of
regurgitation, the test is discontinued unless the ordering
physician instructs to continue the test.
5. Additional Draws/Time Intervals:P
Remaining samples of blood are collected according to the
following
schedule (in minutes after glucose ingestion began):
• At 1/2 hour (30 min. after glucose ingestion) label
GTT30
• At 1 hour (60 min. after glucose ingestion) label GTT60
• At 1-1/2 hours (90 min. after glucose ingestion) label
GTT90
• At 2 hours (120 min. after glucose ingestion) label
GTT120
[NOTE: If M.D.
specifically orders, blood
samples may continue to be obtained on an hourly schedule, up to
6
hours (360 minutes). Reactive hypoglycemia may necessitate the
5-6
hour test schedule.]
6. Storage/Transport:
Samples are kept at room temperature and sent immediately to
Laboratory Service Center.

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

(make the part in blue a link to this document)

UCMC Collection Instructions

To be followed in order as listed below.
1. Patient Fasting: The patient is to eat no food after
midnight
prior to the test (fasting 8-14 hours before test).
2. Fasting Draw: A fasting blood sample should be drawn into a
gray
top Vacutainer tube before Glucocrush® 75 ingestion. Sample
is
labeled Fasting or GTT-FAST.
3. Glucose Beverage Ingestion:
a. Patient drinks the entire bottle of refrigerator-temperature
Glucocrush? 75 solution from a paper cup within 5 minutes. The
patient may pour the Glucocrush? 75 over ice if so desired
b. Timing begins the moment the patient starts drinking.
4. Patient Instructions:
a. A copy of the time schedule will be provided to the patient
and
any differences in collection times will be noted on the
specimen’s label.
b. If patient feels ill, or regurgitates solution, the ordering
physician will be notified immediately. In the case of
regurgitation, the test is discontinued unless the ordering
physician instructs to continue the test.
5. Additional Draws/Time Intervals:P
Remaining samples of blood are collected according to the
following
schedule (in minutes after glucose ingestion began):
• At 1/2 hour (30 min. after glucose ingestion) label
GTT30
• At 1 hour (60 min. after glucose ingestion) label GTT60
• At 1-1/2 hours (90 min. after glucose ingestion) label
GTT90
• At 2 hours (120 min. after glucose ingestion) label
GTT120
[NOTE: If M.D.
specifically orders, blood
samples may continue to be obtained on an hourly schedule, up to
6
hours (360 minutes). Reactive hypoglycemia may necessitate the
5-6
hour test schedule.]
6. Storage/Transport:
Samples are kept at room temperature and sent immediately to
Laboratory Service Center.

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

(make the part in blue a link to this document)

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.
Doses for children are based on patient weight (1.75 g/kg ideal
body weight, not to exceed 75 grams). However, GTTs on children are
ordinarily performed by the Department of Pediatrics in the
University of Chicago Children’s Hospital.

Critical Results

<40 mg/dL
>500mg/dL

Container/Tube

Gray Top
Na-Fluoride, BD Vacutainer tube or equivalent

Specimen Minimum Volume

0.2mL

Day(s) Performed

24 hours, 7 days a week including holidays.

STAT DAY(S) AND TIME(S) PERFORMED

Not Available

Method Name

Spectrophotometric, Kinetic (hexokinase)

Reference Values

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.

Reject Due To

N/A

Stability: Room Temp

8 hours

Stability: Refrigerated

72 hours

Stability: Frozen

Not Stable

Pediatric Volume

0.2mL

Clinical Indications

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.
Doses for children are based on patient weight (1.75 g/kg ideal
body weight, not to exceed 75 grams). However, GTTs on children
are
ordinarily performed by the Department of Pediatrics in the
University of Chicago Children�??s Hospital.

Transport Instructions

To be followed in order as listed below.
1. Patient Fasting: The patient is to eat no food after
midnight
prior to the test (fasting 8-14 hours before test).
2. Fasting Draw: A fasting blood sample should be drawn into a
gray
top Vacutainer tube before Glucocrush?? 75 ingestion. Sample
is
labeled Fasting or GTT-FAST.
3. Glucose Beverage Ingestion:
a. Patient drinks the entire bottle of refrigerator-temperature
Glucocrush? 75 solution from a paper cup within 5 minutes. The
patient may pour the Glucocrush? 75 over ice if so desired
b. Timing begins the moment the patient starts drinking.
4. Patient Instructions:
a. A copy of the time schedule will be provided to the patient
and
any differences in collection times will be noted on the
specimen�??s label.
b. If patient feels ill, or regurgitates solution, the ordering
physician will be notified immediately. In the case of
regurgitation, the test is discontinued unless the ordering
physician instructs to continue the test.
5. Additional Draws/Time Intervals:P
Remaining samples of blood are collected according to the
following
schedule (in minutes after glucose ingestion began):
�?� At 1/2 hour (30 min. after glucose ingestion) label
GTT30
�?� At 1 hour (60 min. after glucose ingestion) label GTT60
�?� At 1-1/2 hours (90 min. after glucose ingestion) label
GTT90
�?� At 2 hours (120 min. after glucose ingestion) label
GTT120
[NOTE: If M.D.
specifically orders, blood
samples may continue to be obtained on an hourly schedule, up
to
6
hours (360 minutes). Reactive hypoglycemia may necessitate the
5-6
hour test schedule.]
6. Storage/Transport:
Samples are kept at room temperature and sent immediately to
Laboratory Service Center.

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

(make the part in blue a link to this document)

Test Components

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.

Specimen Stability

8 hours

Methodology

Spectrophotometric, Kinetic (hexokinase)