ARUP's Laboratory Test Directory

Valproic Acid, Free and Total : 0099310

Mnemonic: VPA-F

Methodology: Quantitative Enzyme Multiplied Immunoassay Technique
Performed: Mon-Fri
Reported: 1-4 days
Specimen Required: Patient Prep: Timing of specimen collection: Pre-dose (trough) draw - At steady state concentration.

Collect: Plain red. Also acceptable (avoid if possible): Serum separator tube (follow preparation instructions below).

Specimen Preparation: Separate serum from cells within 2 hours of collection. Transfer 2 mL serum to an ARUP Standard Transport Tube. (Min: 1 mL)
SST: Serum in a gel separator tube stored at room temperature is acceptable if separated from the gel within 2 hours. Serum in a gel separator tube stored refrigerated is acceptable if separated from the gel within 1 hour.

Storage/Transport Temperature: Refrigerated.

Unacceptable Conditions: Citrated plasma. Tubes that contain liquid anticoagulant.

Stability (collection to initiation of testing): After separation from cells: Ambient: 24 hours; Refrigerated: 1 week; Frozen: 4 months
Reference Interval:
Effective February 19, 2013
 
Test Number Components Therapeutic Range
 Valproic Acid, Total Therapeutic Range: 50-125 µg/mL
Toxic: Greater than 150 µg/mL
 Valproic Acid, Free Therapeutic Range: 5-15 µg/mL
Toxic: Greater than 15 µg/mL
 VPA- % Free 5-18%

Interpretive Data: Free valproic acid may be important to monitor in patients with altered or unpredictable protein binding capacity because valproic acid exhibits variable, dose-dependent protein binding.  Valproic acid is also subject to drug-drug interactions due to displacement of protein binding.  Calculating percent free attempts to minimize differences in test cross-reactivity and may be useful in dose optimization.
CPT Code(s): 80164
Cross References: Depacon (Valproic Acid, Free & Total), Depakene, Free (Valproic Acid, Free & Total), Depakote, Free (Valproic Acid, Free & Total), Dipropylacetic Acid (Valproic Acid, Free & Total), Divalproex (Valproic Acid, Free & Total), Eplim (Valproic Acid, Free & Total), Free Valproate (Valproic Acid, Free & Total), Free Valproic Acid (Valproic Acid, Free & Total), Free VPA (Valproic Acid, Free & Total), Orlept (Valproic Acid, Free & Total), Protein Free Valproic Acid (Valproic Acid, Free & Total), Stavzor, Free (Valproic Acid, Free and Total), Valproate (Valproic Acid, Free & Total)