|Values are valid only on day of printing.|
Detection and quantitation of inhibitors against coagulation factor V
Factor V inhibitors can occur in patients with congenital factor V deficiency after transfusion of fresh frozen plasma, however, more commonly, they occur spontaneously in previously healthy older patients who have no underlying diseases. Topical bovine thrombin or fibrin glue, which contain bovine thrombin and factor V, are commonly used in surgery for topical hemostasis, can result in development of anti-bovine thrombin/factor V inhibitors that cross-react with human thrombin and factor V. Other associations include antibiotics, transfusions and malignancies.
FACTOR V ACTIVITY ASSAY
Normal, full-term newborn infants may have borderline low or mildly decreased levels (> or =30-35%) which reach adult levels within 21 days postnatal.*
Healthy premature infants (30-36 weeks gestation) may have borderline low or mildly decreased levels.*
*See Pediatric Hemostasis References in Coagulation Studies in Special Instructions.
FACTOR V INHIBITOR SCREEN
Normally, there is no inhibitor, ie, negative.
If the screening assays indicate the presence of an inhibitor, it will be quantitated and reported in Bethesda (or equivalent) units.
If the presence or type of inhibitor is unknown, LUPPR / Lupus Anticoagulant Profile should be ordered, except for screening studies in patients with known hemophilia A or B.
Occasionally, a potent lupus-like anticoagulant may cause false-positive testing for a specific factor inhibitor (eg, factor VIII or IX); see preceding Caution statement.
Not useful for the detection of a lupus-like circulating anticoagulant inhibitor or other inhibitors not specific for coagulation factors.
Not useful for the detection of a non specific circulating anticoagulant.
1. Feinstein DI: Acquired inhibitors of blood coagulation. In Hematology: Basic Principles and Practice. Edited by R Hoffman, EJ Benz Jr, SJ Shattil, et al. New York, Livingstone Press, 1991, pp 1380-1394
2. Kasper CK: Treatment of factor VIII inhibitors. Prog Hemost Thromb 1989;9:57-86