Glucagon
Label Mnemonic: GLUN
Epic Lab Code: LAB3217
Downtime Form: A-1a Miscellaneous Request
Commercial Mail-out Laboratory
5231 RCP
356-8593
Specimen(s):
Plasma
Specimen Instructions:
Prechill Pink EDTA tube.
(Overnight fasting is required).
Collection Medium:
Pink top tube 6 mL (K2-EDTA)
Minimum:
Preferred Minimum: 2 mL plasma
Absolute Minimum: 0.45 mL plasma
Delivery Instructions:
Mix well and place on wet ice. Keep on ice and deliver to laboratory immediately.
Turn Around Time:
4 working days upon receipt at reference laboratory
Reference Range:
< or =6 hours: 100-650 pg/mL
1-2 days: 70-450 pg/mL
2-4 days: 100-650 pg/mL
4-14 days: declining gradually to adult levels
>14 days: < or =80 pg/mL (range based on 95% confidence limits)

Glucagon levels are inversely related to blood glucose levels at all ages. This is particularly pronounced at birth and shortly thereafter, until regular feeding patterns are established.
Comments:
Useful For:
Diagnosis and follow-up of glucagonomas and other glucagon- producing tumors.

Assessing diabetic patients with problematic hyper- or hypoglycemic episodes (extremely limited utility).

Glucagon is routinely measured along with serum glucose, insulin, and C- peptide levels, during the mixed-meal test employed in the diagnostic workup of suspected postprandial hypoglycemia. However, it plays only a minor role in the interpretation of this test.

Cautions:
Results obtained with different glucagon assays can differ substantially. This can be caused by use of different calibration standards. Different glucagon assays may also exhibit variable cross- reactivity with different isoforms of glucagon, not all of which are biologically active. Some assays, including this one, remove biologically inactive isoforms before measurement, while others do not. All these factors contribute to the differences between different assays. Serial measurements should, therefore, always be performed using the same assay.

Precise reference ranges for appropriate glucagon responses for given blood glucose ranges are not well established and vary widely from assay to assay. Expert advice should be sought when interpreting inappropriately low glucagon levels or when interpreting glucagon, insulin, and C-peptide levels obtained during mixed-meal testing.

Tumor marker tests, including glucagon, are not specific for malignancy. All immunometric assays can, on rare occasions, be subject to hooking at extremely high analyte concentrations (false-low results), heterophilic antibody interference (false-high results), or autoantibody interference (unpredictable effects). If the laboratory result does not fit the clinical picture, these possibilities should be considered.
Methodology:
Immunoassay Following Extraction
CPT Code:
82943