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HelpOrder Code INSFT Insulin, Free and Total, Serum
Useful For
Assessing free (bioactive) insulin concentrations in patients with known or suspected anti-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 (ECLIA)
Reporting Name
Insulin, Free and Total, SSpecimen Type
SerumSpecimen Required
Patient Preparation:
1. Fasting (8 hours)
2. For 12 hours before specimen collection do not take multivitamins or dietary supplements containing biotin (vitamin B7), which is commonly found in hair, skin, and nail supplements and multivitamins.
Collection Container/Tube:
Preferred: Serum gel
Acceptable: Red top
Submission Container/Tube: Plastic vial
Specimen Volume: 2.45 mL
Collection Instructions:
1. Avoid hemolysis
2. Label specimens with corresponding collection times.
3. Serum-gel tubes should be centrifuged within 2 hours of collection.
4. Red-top tubes should be centrifuged and aliquoted within 2 hours of collection.
5. Send specimen refrigerated
Additional Information: If multiple specimens are collected, send separate order for each specimen.
Specimen Minimum Volume
0.75 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum | Refrigerated (preferred) | 14 days | |
| Frozen | 180 days | ||
| Ambient | 24 hours |
Reject Due To
| Gross hemolysis | Reject |
| Gross lipemia | OK |
| Gross icterus | OK |
| Autopsy/postmortem specimen | Reject |
Reference Values
FREE INSULIN:
3-25 mcIU/mL
TOTAL INSULIN:
3-25 mcIU/mL
Method Description
The Roche cobas insulin method is a sandwich electrochemiluminescence immunoassay that employs a biotinylated monoclonal insulin-specific antibody and a monoclonal insulin-specific antibody. Insulin in the specimen reacts with both the biotinylated monoclonal insulin-specific antibody (mouse) and the monoclonal insulin-specific antibody (mouse) labeled with a ruthenium complex, forming a sandwich complex. Streptavidin-coated microparticles are added, and an interaction occurs between the biotin and streptavidin, binding the complex to the solid phase. The mixture is aspirated into the measuring cell where the microparticles are magnetically captured onto the surface of the electrode. Unbound substances are then removed with ProCell. Application of voltage to the electrode induces the chemiluminescent emission, which is then measured. (Package insert: Insulin reagent, Roche Diagnostics; 2022)
For free insulin, specimen immunoglobulins and their bound insulin are filtered out using a centrifugal ultrafiltration device with a molecular weight cut-off of 125,000 daltons. The filtrate, containing free insulin alone, is analyzed using the method described above.
Day(s) Performed
Monday, Wednesday, Friday
Performing Laboratory
Mayo Clinic Laboratories in Rochester
CPT Code Information
83527-Free Insulin
83525-Total Insulin