Carbamazepine, Free and Total, Serum
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Monitoring carbamazepine therapy in uremic patients
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|
|CARFR||Carbamazepine, Free, S||No||Yes|
|CART||Carbamazepine, Tot, S||Yes||Yes|
CARFR: Membrane Separation/Immunoassay
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Carbamazepine, Free and Total, S
Carbamazepine (Carbatrol, Tegretol)
Free and Total Carbamazepine
Free and Total Carbamazepine
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Container/Tube: Red top
Specimen Volume: 3 mL
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Mild OK; Gross reject
Mild OK; Gross reject
Mild OK; Gross OK
Serum gel tube
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
|Serum Red||Refrigerated (preferred)||14 days|
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
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, the carbamazepine that circulates in blood is 75% 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 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.
Therapeutic concentration: 4.0-12.0 mcg/mL
Toxic concentration: > or =15.0 mcg/mL
Therapeutic concentration: 1.0-3.0 mcg/mL
Toxic concentration: > or =4.0 mcg/mL
In patients with normal renal function, optimal response is often associated with free (unbound) carbamazepine levels >1.0 mcg/mL, and toxicity may occur when the free carbamazepine is > or =4.0 mcg/mL.
In uremic patients, the free carbamazepine level may be a more useful guide for dosage adjustments than the total level. In patients with severe uremia, subtherapeutic total carbamazepine levels in the range of 1.0 to 2.0 mcg/mL may be associated with therapeutic free levels. Toxicity may occur in these patients when the free carbamazepine level is > or =4.0 mcg/mL (even though the total carbamazepine concentration is <15.0 mcg/mL).
As with the serum levels of other anticonvulsant drugs, total and free carbamazepine levels should be correlated with the patient's clinical condition. They are best used as a guide in dose adjustment.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Fresh serum with normal protein content is required for optimal analysis, although serum stored at 4 degrees C for <7 days is acceptable.
Specimens subjected to significant heat or other factors that cause protein denaturation demonstrate an artifactually increased free carbamazepine.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Svinarov DA, Pippenger CE: Relationships between carbamazepine-diol, carbamazepine-epoxide, and carbamazepine total and free steady-state concentrations in epileptic patients: the influence of age, sex, and comedication. Ther Drug Monit 1996;18:660-665
2. Bernus I, Dickinson RG, Hooper WD, Eadie MJ: The mechanism of the carbamazepine-valproate interactions in humans. Br J Clin Phamacol 1997;44:21-27
3. Dasgupta A, Volk A: Displacement of valproic acid and carbamazepine from protein binding in normal and uremic sera by tolmetin, ibuprofen, and naproxen: presence of inhibitor in uremic serum that blocks valproic acid-naproxen interactions. Ther Drug Monit 1996;18:284-287
4. Moyer TP: Therapeutic drug monitoring. In Tietz Textbook of Clinical Chemistry. Edited by CA Burtis, ER Ashwood. Fourth edition. Philadelphia, PA. WB Saunders Company 2005 pp 1237-1285
5. Patsalos PN, Berry DJ, Bourgeois BF, et al: Antiepileptic drugs-best practice guidelines for therapeutic drug monitoring: A position paper by the subcommission on therapeutic drug monitoring, ILAE Commission on Therapeutic Strategies. Epilepsia 2008;49(7):1239-1276
Method Description Describes how the test is performed and provides a method-specific reference
Free carbamazepine is isolated from serum by ultrafiltration and quantified by immunoassay. Enzyme-multiplied immunoassay technique (EMIT) performed for both free and total carbamazepine using Olympus analyzer.(Package insert: EMIT Carbamazepine Assay, Syva Company, Siemens Healthcare Diagnostics Inc., Newark, DE, March 2008)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Sunday; 2 p.m.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Same day/1 day
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
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 The location of the laboratory that performs the test
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 Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
|Result ID||Reporting Name||LOINC Code|
|8654||Carbamazepine, Total, S||3432-2|
|15885||Carbamazepine, Free, S||3433-0|