Factor V inhibitor profile, comprehensive

Alphabetical Test listing

Factor V inhibitor profile, comprehensive-994

Factor V inhibitor profile, comprehensive
Bethesda titer
  • Activated partial thromboplastin time (aPTT)
  • Factor V activity
  • Factor V Bethesda titer
  • Prothrombin time (PT)
  • PT 1:1 mix with normal plasma
  • PT 1:1 mix with saline

Confirmation and characterization of factor V inhibitor


The patient should not be on anticoagulant therapy

Sodium citrate (Na cit) plasma
6 mL (2 mL in each of three tubes)

Do not draw from an arm with a heparin lock or heparinized catheter

  1. Double spin
  2. Transfer 2 mL of plasma into three (3) separate Screw-cap polypropylene frozen transport vial/tube - 4mL (LabCorp) labelled as Na cit plasma
  3. FREEZE immediately and maintain frozen until tested.

Frozen (preferred) – 30 days

Ambient – 4 hours

Refrigerated – NO

LabCorp Esoterix Coag Laboratory (500380): R – NX
Mo – Th, Sat
3 – 5 days

The factor V inhibitor (Bethesda titer) assay is performed using a prothrombin time-based system, using thromboplastin reagent.6 Serial dilutions are made of patient plasma with veronal buffered saline, then mixed with normal plasma containing close to 100% factor V activity, and are then incubated for two hours. A PT-based factor V assay using factor V-depleted plasma substrate is then performed on these incubated mixtures. Results are compared to those of incubated normal plasma. One Bethesda unit is defined as the amount of factor V inhibitor that neutralized 0.5 IU of factor V in this system. The number of serial dilutions tested is based on the anticipated level of the inhibitor.


Prothrombin and APTT, sec

Factor V activity, % and Facator V inact assay, <0.8 Bethesda

85611 x 2