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HelpTest ID CARFT Carbamazepine, Free and Total, Serum
Specimen Required
Container/Tube: Red top (serum gel/SST are not acceptable)
Submission Container/Tube: Plastic vial
Specimen Volume: 2 mL
Collection Instructions: Centrifuge and aliquot serum into a plastic vial within 2 hours of collection.
Forms
If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.
Secondary ID
37039Useful For
Monitoring carbamazepine (free and total) therapy in patients who are uremic
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| CARTA | Carbamazepine, Tot, S | Yes | Yes |
| CARF | Carbamazepine, Free, S | Yes | Yes |
Method Name
CARF: Ultrafiltration Followed by Homogeneous Microparticle Agglutination Immunoassay
CARTA: Homogeneous Microparticle Agglutination Immunoassay
Reporting Name
Carbamazepine, Free and Total, SSpecimen Type
Serum RedSpecimen Minimum Volume
1 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum Red | Refrigerated (preferred) | 7 days |
| Frozen | 28 days | |
| Ambient | 48 hours |
Clinical Information
Carbamazepine (Tegretol) is an effective treatment for complex partial seizures, with or without generalization to tonic-clonic seizures. It is frequently administered in conjunction with other antiepileptic agents, such as phenytoin and valproic acid.
Under normal circumstances, 75% of the carbamazepine that circulates in blood is protein bound. In severe uremia, carbamazepine may be displaced from protein, resulting in a higher free (unbound) fraction of the drug circulating in blood. Since neurologic activity and toxicity are directly related to the circulating free fraction of drug, adjustment of dosage based on knowledge of the free carbamazepine level may be useful in patients with severe uremia.
Reference Values
CARBAMAZEPINE, TOTAL
Therapeutic: 4.0-12.0 mcg/mL
Critical value: ≥15.0 mcg/mL
CARBAMAZEPINE, FREE
Therapeutic: 1.0-3.0 mcg/mL
Critical value: ≥4.0 mcg/mL
Cautions
Fresh serum with normal protein content is required for optimal analysis.
Specimens subjected to significant heat or other factors that cause protein denaturation demonstrate an artifactually increased free carbamazepine.
If hemolysis, lipemia, or icterus exceed the analytical interference threshold, the testing will be canceled.
Day(s) Performed
Monday through Sunday
Report Available
Same day/1 dayPerforming Laboratory
Mayo Clinic 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 US Food and Drug Administration.CPT Code Information
80156
80157