Name: Valproate, Unbound
Test Name: Valproate, Unbound
Health Link Test Code: HCUVATE
LIS Test Code: UVATE
CPT Code(s): 80164, 80165
Total and unbound (free) valproic acid.
Methodology: Gas Chromatography
Days Performed: Daily, dayshift- unbound level is not available after hours.
In-Lab Turnaround Time: 1 day.
Stat In-Lab Turnaround Time: 2 hours.
Collection Container: Red top
Collection Volume: 9 mL
Pediatric Collection Volume: 3 mL
Sample Analyzed: Serum
Testing Volume: 2 mL
Pediatric Testing Volume: 1 mL
Centrifuge. Transfer cell-free serum to plastic vial. Refrigerate.
Transport specimen to laboratory. Transport with coolant pack if coming from clinic location.
Specimens collected in red cap with yellow ring (SST) tubes are not acceptable.
The therapeutic range for unbound valproate has not been established. The free fraction should be 7-15% when the total valproate is 50-100 mcg/mL, and 22-30% when the total is 125-150 mcg/mL.
Interpretation Type: Interpretive Guidelines
Critical Calls: yes
Protein binding of valproic acid is concentration dependent. Albumin sites will be saturated, in most individuals, when the total valproic acid level is near 100 mcg/mL. Any increase in dose will markedly increase the free drug level. The free fraction will increase in the presence of hypoalbuminemia. Free fatty acids may cause increased free valproate fraction.
This test was developed and its performance characteristics determined by the UWHC Clinical Laboratories. This test meets the standards for clinical testing. This test should not be regarded as investigational or for research use. The US Food and Drug Administration (FDA) has not approved or cleared this test; however, the FDA has determined that such clearance or approval is not necessary.