Insulin, Free and Total, Serum
Use
This test is useful for assessing free (bioactive) insulin concentrations in patients with known or suspected anti-insulin antibodies. It helps to distinguish between free insulin and insulin bound by autoantibodies, providing a measure of biologically active insulin. This information can aid in understanding patient symptoms related to hypoglycemia or insulin resistance when anti-insulin antibodies are present.
Special Instructions
Patients undergoing this test should fast for 8 hours before specimen collection. Additionally, they should avoid taking multivitamins or dietary supplements containing biotin (vitamin B7) for 12 hours prior to collection. The test distinguishes between free and total insulin concentrations to detect the presence of anti-insulin antibodies.
Limitations
This assay does not detect insulin analogues such as insulin lispro, aspart, or glargine. It has cross-reactivity with recombinant human insulin but is affected by hemolysis, as it releases insulin-degrading enzymes from erythrocytes. The presence of human anti-mouse antibodies or antibodies against streptavidin/ruthenium may also interfere with the results, warranting cautious interpretation in such scenarios.
New York Approved
Methodology
Immunoassay (ECLIA)
Biomarkers
LOINC Codes
- 48615-9
- 27873-9
- 6901-3
Result Turnaround Time
1-4 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
2.45 mL
Minimum Volume
0.75 mL
Container
Serum gel or Red top, submitted in Plastic vial
Collection Instructions
Avoid hemolysis, label specimens with collection times. Serum-gel tubes need centrifugation within 2 hours of collection. Send specimens refrigerated. Each specimen collected should be ordered separately.
Patient Preparation
Fasting required for 8 hours. Avoid multivitamins or supplements containing biotin for 12 hours before collection.
Causes for Rejection
Gross hemolysis or autopsy/postmortem specimens are cause for rejection.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 24 hours |
| Refrigerated | 14 days |
| Frozen | 180 days |