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HelpOrder Code VALPG Valproic Acid, Free and Total, Serum
Useful For
Monitoring both total and free valproic acid levels in therapy
Assessing compliance
Evaluating potential toxicity
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| VALPF | Valproic Acid, Free, S | Yes | Yes |
| VALPA | Valproic Acid, Tot, S | Yes | Yes |
Method Name
VALPA: Immunoassay
VALPF: Ultrafiltration Followed by Immunoassay
Reporting Name
Valproic Acid, Free and Total, SSpecimen Type
SerumSpecimen Required
Collection Container/Tube:
Preferred: Serum gel
Acceptable: Red top
Submission Container/Tube: Plastic vial
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 the serum aliquoted into a plastic vial 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
VALPROIC ACID, TOTAL
Therapeutic: 50 (trough)-125 (peak) mcg/mL
Critical value: ≥151 mcg/mL
VALPROIC ACID, FREE
Therapeutic: 5-25 mcg/mL
Critical value: >30 mcg/mL
Method Description
The assay is based on a homogeneous enzyme immunoassay technique used for the quantitative analysis of valproic acid (free and protein-bound) in human serum or plasma. The assay is based on competition between drug in the sample and drug labeled with the enzyme glucose-6-phosphate dehydrogenase (G6PD) for antibody binding sites. Enzyme activity decreases upon binding to the antibody, so the drug concentration in the sample can be measured in terms of enzyme activity. Active enzyme converts oxidized nicotinamide adenine dinucleotide (NAD+) to NADH, resulting in an absorbance change that is measured spectrophotometrically. Endogenous serum G6PD does not interfere because the coenzyme functions only with the bacterial (Leuconostoc mesenteroides) enzyme employed in the assay.(Package insert: Valproic Acid reagent. Roche Diagnostics; 04/2018)
Day(s) Performed
Monday through Sunday
Performing Laboratory
Mayo Clinic Laboratories in Rochester
CPT Code Information
VALPA-80164
VALPF-80165
Forms
If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.