Insulin, Free and Total
Use
Most patients receiving insulin will eventually form antibodies that bind insulin. These antibodies may or may not affect the activity and metabolism of insulin. Laboratory tests may be used to identify patients with insulin antibodies, for instance LabCorp test 141598. Patient antibodies may affect the normal insulin measurements. Free and total insulin is a test to measure the fraction of insulin that is bound by antibodies and to measure total insulin after the removal of antibodies by special preparation.
Special Instructions
Sequential free insulin measurements are useful to evaluate possible abnormal insulin absorption after subcutaneous injection. In this case, the presence of insulin-binding antibodies can alter the pharmacokinetics of insulin and lead to an abnormal period of hyperglycemia in response to a delayed increase in the free fraction.
Limitations
Measurement is performed on acid-treated samples and, therefore, the sensitivity and absolute values by this method may differ from direct insulin immunoassays. The specificity and avidity of antibodies can affect the test. In patients with significant levels of antibodies, the bound fraction of insulin accounts for more than 90% of the total insulin. Cross-reactivity of modern insulin analogs with the immunoassay should be taken into account, as drugs like insulin glulisine and insulin detemir show lower cross-reactivity.
Methodology
Immunoassay (CLIA)
Biomarkers
LOINC Codes
- 48615-9
- 6901-3
- 20448-7
Result Turnaround Time
5-12 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
3 mL (adult and pediatric)
Minimum Volume
1.5 mL
Container
Red-top tube or gel-barrier tube
Collection Instructions
Submit serum in a plastic transport tube
Storage Instructions
Refrigerate.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 2 days |
| Refrigerated | 10 days |
| Frozen | 200 days |