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HelpTest ID INSFT Insulin, Free and Total, Serum
Useful For
Assessing free (bioactive) insulin concentrations in patients with known or suspected insulin antibodies
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| INSF | Insulin, Free, S | No | Yes |
| INSTO | Insulin, Total, S | Yes, (Order as INS) | Yes |
Method Name
Electrochemiluminescence Immunoassay
Reporting Name
Insulin, Free and Total, SSpecimen Type
SerumCollection Container/Tube:
Preferred: Red top
Acceptable: Serum gel
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Collection Instructions:
1. Fasting (8 hours)
2. Avoid hemolysis
3. Label specimens with corresponding draw times.
4. Serum-gel tubes should be centrifuged within 2 hours of collection.
5. Red-top tubes should be centrifuged and aliquoted within 2 hours of collection.
6. Send frozen to laboratory
Additional Information: If multiple specimens are drawn, send separate order for each specimen.
Specimen Minimum Volume
0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum | Frozen (preferred) | 180 days |
| Refrigerated | 7 days |
Clinical Information
Insulin is produced by the beta cells of the pancreas. It regulates the uptake and utilization of glucose and is also involved in protein synthesis and triglyceride storage.
Circulating insulin antibodies develop after diabetic patients are treated with exogenous insulin preparations. The presence of insulin antibodies has 2 main consequences:
1. Insulin antibodies will directly bind to insulin, making it unavailable for metabolic activity.
2. Insulin antibodies may adversely affect the binding characteristics of insulin in immunoassays, making reliable quantitation difficult.
Free (bioactive) insulin could be measured after polyethylene glycol (PEG) precipitation of insulin antibodies and their bound insulin. If insulin antibodies are not present, the free and total insulin should be equivalent. The laboratory will report results of the total insulin (without PEG precipitation) and the free insulin (with PEG precipitation).
Reference Values
Insulin, Free, S
2.6-24.9 mcIU/mL
Insulin, Total, S
2.6-24.9 mcIU/mL
Cautions
Human anti-mouse antibodies (HAMA) may interfere with the assay.
In patients receiving therapy with high biotin doses (ie, >5 mg/day), no sample should be taken until at least 8 hours after the last biotin administration.
Hemolysis interferes, as insulin-degrading peptidases are released from erythrocytes. This assay has 100% cross-reactivity with recombinant human insulin (Novolin R and Novolin N). It does not recognize other commonly used analogues of injectable insulin (ie, insulin lispro, insulin aspart, and insulin glargine).
Day(s) Performed
Monday through Saturday; Continuously
Report Available
1 dayPerforming Laboratory
Mayo Medical Laboratories in Rochester
Test Classification
This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.CPT Code Information
83527-Free Insulin
83525-Total Insulin