Coagulation Factor VII Inhibitor Screen, Plasma
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
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 VII
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.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
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.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
FACTOR VII ACTIVITY ASSAY
Normal, full-term newborn infants or healthy premature infants may have decreased levels (> or =20%) which increase within the first postnatal week but may not reach adult levels for > or =180 days postnatal.*
*See Pediatric Hemostasis References in Coagulation Studies in Special Instructions.
FACTOR VII INHIBITOR SCREEN
Clinical References Provides recommendations for further in-depth reading of a clinical nature
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