Ordering Recommendation

Optimize drug therapy and monitor patient adherence.

Mnemonic
CARB FT
Methodology

Quantitative Enzyme Multiplied Immunoassay Technique

Performed

Sun-Sat

Reported

1-5 days

New York DOH Approval Status
This test is New York DOH approved.
Specimen Required
Patient Preparation
Collect

Serum Pre-dose (Trough) Draw - At a Steady State Concentration in Plain Red.

Specimen Preparation

Separate from cells ASAP or within 2 hours of collection. Transfer 2 mL serum to an ARUP Standard Transport Tube. (Min: 1 mL)

Storage/Transport Temperature

Refrigerated.

Unacceptable Conditions

Whole Blood, Citrated Plasma. Tubes that contain liquid anticoagulant.or Serum separator tube (SST).

Remarks
Stability

Ambient: 5 days; Refrigerated: 5 days; Frozen: 3 months

Reference Interval

Effective November 16, 2015

Test Number
Components
Reference Interval
  Total Carbamazepine Therapeutic Range: 4.0-12.0 µg/mL
Toxic Range: Greater than 15 µg/mL
  Free Carbamazepine Therapeutic Range: 1.0-3.0 µg/mL
Toxic Range: Greater than 3.8 µg/mL
  Percent Free Carbamazepine 8.0-35.0%

Interpretive Data

The therapeutic range is based on serum pre-dose (trough) draw at steady-state concentration. Free carbamazepine may be important to monitor in patients with altered or unpredictable protein binding capacity. Carbamazepine is also subject to drug-drug interactions due to displacement of protein binding and extensive metabolism. Cross-reactivity with metabolites may account for differences in carbamazepine among analytical methods. Calculating percent free attempts to minimize differences in assay cross-reactivity and may be useful in dose optimization.

A rare adverse drug reaction to carbamazepine therapy includes Stevens-Johnson syndrome or toxic epidermal necrolysis. Patients of Asian ancestry with the presence of the HLA-B*15:02 have an increased risk for this carbamazepine-induced life-threatening reaction. Pharmacogenetic testing for HLA-B*15:02 is recommended for patients at risk for carbamazepine hypersensitivity prior to treatment. This information has been included in the FDA-approved label for carbamazepine (https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&varApplNo=016608) and guideline from the Clinical Pharmacogenetics Implementation Consortium (https://www.pharmgkb.org/guidelines) [ARUP test code 2012049, HLA-B*15:02 Genotyping, Carbamazepine Hypersensitivity.] A combination of therapeutic drug monitoring with HLA-B*15:02 pharmacogenetics genotyping may benefit patients who are at increased risk for developing carbamazepine-induced adverse events due to rare genotypes other than HLA-B*15:02 variant allele.

No compliance statements are in use for this test.

Note
Hotline History
N/A
CPT Codes

80156; 80157

Components
Component Test Code* Component Chart Name LOINC
2011768 Free Carbamazepine 3433-0
2011769 Percent Free Carbamazepine 32852-6
2011770 Total Carbamazepine 3432-2
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.
Aliases
  • Atretol
  • Biston
  • Calesin
  • Carbamazepine, Free
  • Carbatrol
  • Epimaz
  • Epitol
  • Epitrol
  • Equetro
  • Finlepsin
  • Free Carbamazepine
  • Free Tegretol
  • Protein Free Carbamazepine
  • Sirtal
  • Tegretol, Free
  • Telesmin
Carbamazepine, Free and Total, Serum or Plasma