Valproic Acid, Free

Test Code

CPT Codes

Preferred Specimen
3 mL serum collected in a red-top tube (no gel)

Minimum Volume
1 mL

Other Acceptable Specimens
Serum collected in no additive (royal blue-top) tube • Plasma collected in an EDTA (lavender-top), or EDTA (royal blue-top) tube

Do not use gel barrier tubes. Centrifuge and immediately separate serum or plasma specimens from the cells into clean, plastic, screw-cap vial(s). Do not use serum separator tubes. Submission of a serum separator tube will result in cancellation.

Transport Container
Plastic screw-cap vial(s)

Transport Temperature
Refrigerated (cold packs)

Specimen Stability
Room temperature: 48 hours
Refrigerated: 7 days
Frozen: 60 days

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Serum separator tube (SST®)

Fluorescence Polarization Immunoassay (FPIA)

Reference Range
4.8-17.3 mg/L

Detection limit 2.0 mg/L

Nonlinear drug binding properties result in the fraction of free valproic acid increasing as total drug increases. The free fraction may range from 5% to 25% for the total drug range of 30-160 mg/L.

Clinical Significance
Valproic acid is a broad spectrum anticonvulsant for the treatment of absence seizures. It is effective in the management of generalized tonic-econic and myoconic seizures, as well as grand mal and petit mal.

Performing Laboratory
Quest Diagnostics Nichols Institute
14225 Newbrook Drive
Chantilly, VA 20153

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.