Factor V Activity and Human Inhibitor

Test Code

CPT Codes
85220, 85335

Preferred Specimen
2 mL frozen platelet-poor plasma collected in each of two 3.2% sodium citrate (light blue-top) tubes

Minimum Volume
1 mL (x2)

Platelet-poor plasma: Centrifuge light blue-top tube for 15 minutes at approximately 1500 x g within 60 minutes of collection. Using a plastic pipette, remove plasma, taking care to avoid the WBC/platelet buffy layer and place into a plastic vial. Centrifuge a second time and transfer platelet-poor plasma into a new plastic vial. Plasma must be free of platelets (< 10,000/mcL). Freeze immediately and ship on dry ice. Do not thaw.

Transport Container
Plastic screw-cap vials (x2)

Transport Temperature

Specimen Stability
Room temperature: Unacceptable
Refrigerated: Unacceptable
Frozen -20°C: 14 days
Frozen -70°C: 1 year

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Hemolyzed specimens

Clot Based

Setup Schedule
Set up: Tues; Report available: 3-11 days

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.

1. Tabibian S, et al. Semin Thromb Hemost. 2019;45(5):523-543.

Performing Laboratory
Quest Diagnostics Nichols Institute-San Juan Capistrano, CA
33608 Ortega Highway
San Juan Capistrano, CA 92675-2042

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.