Valproic Acid, Free and Total


Abbrev Code:VALPFR   
Order Code:LAB5847Order Name:Valproic Acid Free and Total
Synonyms:Free Depakene; Free Depakote
Methodology:Quantitative enzyme multiplied immunoassay technique
CPT Codes: 80165 x1, 80165 x1, 80164 x1, 80164 x1
Turnaround Time:Routine specimens are sent to reference laboratory Mon-Fri; results are reported within 1-3 days. Stat specimens are sent to the reference laboratory 24/7; results are reported the same day.
Compliance:

This test uses an in vitro diagnostic (IVD) that has been cleared or approved by the FDA.



Collection Instructions

Specimen:Blood
Optimal Volume:4 mL
Minimum\Peds Volume:2.2 mL
Container:Red (no gel)
Collection Instructions:Timing of specimen collection: Pre-dose (trough) draw - At steady state concentration.
Causes for Rejection:Specimens collected in light blue (citrate), gray (oxalate), green (heparin), K2EDTA plasma; tubes that contain liquid anticoagulant, or gel separator tubes.


Processing and Shipping

Specimen Processing:Separate serum from cells within 2 hours of collection and aliquot 2 mL, 1 mL minimium, serum. Store in refrigerator.
Shipping Instructions:Ship at refrigerated temperature.
Stability:After separation from cells: 24 hours at room temperature; 1 week refrigerated; 1 month frozen.
Test Performed at or Referral Lab Lab Sendouts  (ARUP)
Referral Lab number:0099310


Interpretive

Critical Range:
Valproic Acid Total Toxic: Greater than 150 μg/mL
Valproic Acid Free Toxic: Greater than 30 μg/mL*
*Effective November 18, 2013
Reference Range:Valproic Acid Percent Free: 5-18%
Therapeutic Range:
Valproic Acid Total 50-125 μg/mL
Valproic Acid Free 7-23 μg/mL*
  *Effective November 18, 2013
Use:Preferred test for therapeutic drug management in patients with renal failure or conditions that may alter albumin concentrations.

Free valproic acid may be important to monitor 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. Adverse effects may include headache, somnolence and dizziness.


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