ARUP's Laboratory Test Directory

0099310: Valproic Acid, Free & Total

Test Mnemonic: VPA-F
Methodology: Immunoassay

Performed: Mon-Fri

Reported: 1-4 days

Specimen Required:  
Collect: One 5 mL plain red.

Transport: 2 mL serum at 2-8°C.  (Min: 1 mL)  Submit specimen in an ARUP Standard Transport Tube.

Pediatric Collection/Transport: 1 mL serum at 2-8°C.

Remarks: Separate serum from cells ASAP.  Avoid use of separator tubes and gels.  Do not use heparin as an anticoagulant.

Stability: After separation from cells: Ambient: 24 hours; Refrigerated: 1 week; Frozen: 4 months

Reference Interval:
 
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: 6-22 µg/mL
Toxic: Greater than 50 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 assay cross-reactivity and may be useful in dose optimization.



CPT Code(s):
80164 VPA, total; 80164 VPA, free

 

 

 
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