|Values are valid only on day of printing.|
Coagulation factor inhibitors arise in patients who are congenitally deficient in a specific factor in response to factor replacement therapy, or can occur spontaneously without known cause or in response to a variety of medical conditions including the postpartum state, immunologic disorders, certain antibiotic therapies, some malignancies, and old age.
Inhibitors of factor VIII coagulant activity are the most commonly occurring of the specific factor inhibitors.
Detection and quantitation of inhibitor to coagulation factor X
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 nonspecific circulating anticoagulant.
FACTOR X ACTIVITY ASSAY
Normal, full-term newborn infants or healthy premature infants may have decreased levels (> or =15-20%) which may not reach adult levels for > or =180 days postnatal.*
*See Pediatric Hemostasis References in Coagulation Studies in Special Instructions.
FACTOR X INHIBITOR SCREEN
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, NY, Livingstone Press, 1991, pp 1380-1394
2. Kasper CK: Treatment of factor VIII inhibitors. Prog Hemost Thromb 1989;9:57-86