Test Id : INSFT
Insulin, Free and Total, Serum
Useful For
Suggests clinical disorders or settings where the test may be helpful
Assessing free (bioactive) insulin concentrations in patients with known or suspected anti-insulin antibodies
Highlights
Patients treated with exogenous insulin preparations might develop autoantibodies against insulin.
If significant differences between the total and free insulin concentrations are detected following ultrafiltration, the presence of anti-insulin antibodies is suspected.
Profile Information
A profile is a group of laboratory tests that are ordered and performed together under a single Mayo Test ID. Profile information lists the test performed, inclusive of the test fee, when a profile is ordered and includes reporting names and individual availability.
| Test Id | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| INSF | Insulin, Free, S | No | Yes |
| INSTO | Insulin, Total, S | Yes, (Order INS) | Yes |
Method Name
A short description of the method used to perform the test
Electrochemiluminescence Immunoassay (ECLIA)
NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.
Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test
Aliases
Lists additional common names for a test, as an aid in searching
Free Insulin, Serum
Specimen Type
Describes the specimen type validated for testing
Serum
Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing
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
Defines the amount of sample necessary to provide a clinically relevant result as determined by the testing laboratory. The minimum volume is sufficient for one attempt at testing.
0.75 mL
Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected
| Gross hemolysis | Reject |
| Gross lipemia | OK |
| Gross icterus | OK |
| Autopsy/postmortem specimen | Reject |
Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum | Refrigerated (preferred) | 14 days | |
| Ambient | 24 hours | ||
| Frozen | 180 days |
Useful For
Suggests clinical disorders or settings where the test may be helpful
Assessing free (bioactive) insulin concentrations in patients with known or suspected anti-insulin antibodies
Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
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.
Some patients receiving insulin may develop antibodies that bind insulin. These antibodies may or may not affect the activity and metabolism of insulin.
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 ultrafiltration to remove anti-insulin antibodies and their bound insulin. If insulin antibodies are not present, the free and total insulin concentrations should be equivalent. The laboratory will report results of the total insulin (without ultrafiltration) and the free insulin (after ultrafiltration).
Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
FREE INSULIN:
3-25 mcIU/mL
TOTAL INSULIN:
3-25 mcIU/mL
Interpretation
Provides information to assist in interpretation of the test results
Free insulin represents the portion of total insulin unbound by anti-insulin antibodies in the circulation. This fraction serves as a measure of biologically active insulin and provides an indication of the true relationship between insulin and blood glucose.
Most individuals do not have anti-insulin antibodies in circulation and therefore the free and total insulin concentrations would be equivalent.
When a significant difference between total and free insulin Concentrations is observed following ultrafiltration, the result is suggestive of the presence of insulin antibodies. In these cases, confirmation of the presence of anti-insulin antibodies (Mayo Test ID: INAB) may be helpful.
Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
In rare cases, some individuals can develop antibodies to mouse or other animal antibodies (often referred to as human anti-mouse antibodies [HAMA] or heterophile antibodies), which may cause interference in some immunoassays. The presence of antibodies to streptavidin or ruthenium can also rarely occur and may also interfere in this assay. Caution should be used in interpretation of results, and the laboratory should be alerted if the result does not correlate with the clinical presentation.
Hemolysis interferes with this assay, as insulin-degrading peptidases are released from erythrocytes.
Clinical Reference
Recommendations for in-depth reading of a clinical nature
1. Lupsa BC, Chong AY, Cochran EK, Soos MA, Semple RK, Gorden P. Autoimmune forms of hypoglycemia. Medicine (Baltimore). 2009;88(3):141-153
2. Sapin R, Le Galudec V, Gasser F, Pinget M, Grucker D. Elecsys insulin assay: free insulin determination and the absence of cross-reactivity with insulin lispro. Clin Chem. 2001;47(3):602-605
3. Sacks DB: Diabetes mellitus. In: Rifai N, Horvath AR, Wittwer CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics 6th ed. Elsevier; 2018:1160-1200
Method Description
Describes how the test is performed and provides a method-specific reference
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.
PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information
Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.
Monday, Wednesday, Friday
Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.
Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location
Indicates the location of the laboratory that performs the test
Fees :
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.
- Authorized users can sign in to Test Prices for detailed fee information.
- Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
- Prospective clients should contact their account representative. For assistance, contact Customer Service.
Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.
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 US Food and Drug Administration.
CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
CPT codes are provided by the performing laboratory.
CPT codes are provided by the performing laboratory.
83527-Free Insulin
83525-Total Insulin
LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.
| Test Id | Test Order Name | Order LOINC Value |
|---|---|---|
| INSFT | Insulin, Free and Total, S | 48615-9 |
| Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
|---|---|---|
| INSTO | Insulin, Total, S | 20448-7 |
| INSF | Insulin, Free, S | 6901-3 |