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Test Code VALPF Valproic Acid, Free, Serum

Reporting Name

Valproic Acid, Free, S

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Useful For

Monitoring free valproic acid in therapy

 

Assessing compliance

 

Evaluating potential toxicity

Method Name

Ultrafiltration Followed by Immunoassay

Specimen Type

Serum


Specimen Required


Container/Tube:
Preferred:
Serum gel
Acceptable: Red top
Specimen Volume: 2 mL
Collection Instructions:
1. Serum gel tubes should be centrifuged within 2 hours of collection.
2. Red-top tubes should be centrifuged and aliquoted within 2 hours of collection.


Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 14 days
  Frozen  28 days
  Ambient  72 hours

Reject Due To

Gross hemolysis Reject

Reference Values

Therapeutic: 5-25 mcg/mL

Critical value: >30 mcg/mL

Interpretation

The generally acceptable range for total valproic acid used as a reference to guide its therapy is 50 to 125 mcg/mL. The corresponding range of free valproic acid concentration for clinical reference is 5 to 25 mcg/mL.

 

Low free valproic acid concentration relative to these ranges may suggest inadequate dosing, whereas, a high free valproic acid concentration may be associated with toxic effects.

 

Because the concentration of valproic acid fluctuates considerably depending on the time from last dose, interpretation of the clinical significance of the valproic acid concentration must take into consideration the timing of the blood specimen. For this reason, 2 collections are sometimes made to assess the trough and peak concentrations.

Day(s) and Time(s) Performed

Monday through Sunday; Continuously

Test Classification

This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

80165

LOINC Code Information

Test ID Test Order Name Order LOINC Value
VALPF Valproic Acid, Free, S 4087-3

 

Result ID Test Result Name Result LOINC Value
VALPF Valproic Acid, Free, S 4087-3

Forms

If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.