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Factor V Activity and Human Inhibitor
Test CodeCPT Codes
85220, 85335
Preferred Specimen
Minimum Volume
Instructions
Transport Container
Transport Temperature
Specimen Stability
Refrigerated: Unacceptable
Frozen -20°C: 14 days
Frozen -70°C: 1 year
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Methodology
Clot Based
Setup Schedule
Reference Range
Factor V Activity | 65-150 | % normal |
Factor V Human Inhibitor | ≤0.4 | BU |
Clinical Significance
This panel quantifies coagulation factor V activity and inhibitors to factor V and may be used to support the diagnosis of factor V deficiency as a result of inhibitor development.
Coagulation factor V plays an essential role in hemostasis by promoting thrombin generation at the activated platelet surface. Deficiency of factor V leads to a rare bleeding disorder and can be congenital or acquired. Congenital factor V deficiency is caused by pathogenic variants of the F5 gene, while acquired factor V deficiency can be caused by liver disease, consumptive coagulopathies, disseminated intravascular coagulation, or inhibitors (autoantibodies or alloantibodies) that interfere with factor V activity. Inhibition of factor V activity secondary to antibody development is a rare occurrence and may be induced by chemical agents, drugs, or surgical procedures using bovine thrombin [1].
Patients with inhibitors to factor V usually have prolonged prothrombin time (PT) and activated partial thromboplastin time (aPTT), low factor V activity levels, and a normal thrombin time. Factor V inhibitors are measured using a Bethesda assay and are reported in Bethesda titer units (BU). Quantification of factor V inhibitors may inform treatment decisions for acquired factor V deficiency and help monitor inhibitor suppression therapy [1].
The results of this test should be interpreted in the context of pertinent clinical and family history and physical examination findings.
Reference
1. Tabibian S, et al. Semin Thromb Hemost. 2019;45(5):523-543.