Coagulation Factor XI Inhibitor Screen, Plasma
Detection and quantitation of inhibitor to coagulation factor XI
Testing Algorithm Delineates situation(s) when tests are added to the initial order. This includes reflex and additional tests.
If appropriate, a Bethesda titer will be performed at an additional charge to quantify the inhibitor.
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Factor XI inhibitors typically arise in patients with congenital XI deficiency (hemophilia C), after infusion of fresh frozen plasma or factor XI concentrates. Acquired factor XI inhibitors rarely occur spontaneously.
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 XI ACTIVITY ASSAY
Normal, full-term newborn infants or healthy premature infants may have decreased levels (> or =10%) which may not reach adult levels for > or =180 days postnatal.*
*See Pediatric Hemostasis References in Coagulation Studies in Special Instructions.
FACTOR XI 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.
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 nonspecific circulating anticoagulant.
Clinical Reference 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