Glucose Tolerance Test-2 HR

Label Mnemonic:	GT20
Epic code:	LAB169
Downtime form:	Doctor/Provider Orders - Pathology Core and Specialty Care Nursery

Chemistry
6240 RCP
356-3527

Specimen(s):

Plasma

Collection Medium:

Gray top tube 6 mL (Na Fluoride)

Alternate Collection Media:

Call laboratory for additional acceptable specimen collection containers.

Minimum:

3 mL; gray (sodium fluoride) top (or ONE microtube for pediatric patients) per specimen.

Testing Schedule:

24 hrs/day, 7 days a week, including holidays.

Turn Around Time:

1 hour (upon receipt in laboratory)

Reference Range:

If testing is intended for evaluation of gestational diabetes, consider use of the GTT 2 Hour (100 gram dose for pregnancy) [LAB8762] test.

General {Non-pregnant/Non-Postpartum}: < 155 mg/dL

Reference range for non-pregnancy glucose tolerance test using 75 g glucose.

Two-hour plasma glucose concentration:
< 140 mg/dL: normal
140-199 mg/dL: impaired glucose tolerance
200 mg/dL or higher: diabetes

Reference: Classification and Diagnosis of Diabetes: Standards of Medical Care in Diabetes—2020. American Diabetes Association. Diabetes Care 2020 Jan; 43(Supplement 1): S14-S31.

Comments:

Collect all specimens in gray top tube on patient care area and 
hold (sodium fluoride anticoagulant).  Deliver all specimens 
simultaneously.  Microtube specimens must be scheduled with the lab in 
advance and delivered immediately after drawing.

Two hour Glucose Tolerance Test should include the following 
specimens:
  Fasting glucose
  1 hour post glucose
  2 hour post glucose

Test Limitations:

Icterus: No significant interference up to an I index of 60 
(approximate conjugated and unconjugated bilirubin concentration: 
60 mg/dL).

Hemolysis: No significant interference up to an H index of 1000 
(approximate hemoglobin concentration 1000 mg/dL).

Lipemia (Intralipid): No significant interference up to an L index of 
1000 (approximate triglycerides concentration 2000 mg/dL). There is 
poor correlation between turbidity and triglycerides 
concentration.

Methodology:

Hexokinase/UV Test

CPT Code:

82951 for the first 3 specimens and 82952 for each additional specimens

See Additional Information:
Specimens Requiring Immediate Delivery
Fasting Specimen Requirements