Mayo Test Catalog, (Sorted By Test Name) - Mayo Medical ...

F5DNA
81419
factor IX in patients with hemophilia B
Interpretation: Normally, there is no inhibitor (ie, negative result). If the screening assays indicate
the presence of an inhibitor, it will be quantitated and reported in Bethesda (or equivalent) units.
Reference Values:
FACTOR IX ACTIVITY ASSAY
Adults: 65-140%
Normal, full-term newborn infants or healthy premature infants may have decreased levels (> or
=20%), which may not reach adult levels for > or =180 days postnatal.*
*See Pediatric Hemostasis References in Coagulation Studies in Special Instructions.
FACTOR IX INHIBITOR SCREEN
Negative
BETHESDA TITER
0 Units
Clinical References: 1. Feinstein DI, Rapaport, SI: 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. Chitlur M, Warrier I, Rajpurkar M, et al: Inhibitors in
factor IX deficiency a report of the ISTH-SSC international FIX inhibitor registry (1997-2006).
Haemophilia 2009;15(5):1027-1031
Factor V Leiden (R506Q) Mutation, Blood
Clinical Information: Venous thromboembolism (VTE) is a syndrome of deep vein thrombosis and
its complication, pulmonary embolism. Recent work highlights the role of both genetic heterogeneity
and genetic:environmental interaction in the etiology of VTE.(1) Plasma from 12% to 52% of VTE
patients is resistant to the anticoagulant effect of activated protein C (APC-resistance).(2)
Approximately 90% of patients with hereditary APC-resistance have a single nucleotide mutation of the
coagulation factor V gene that encodes for an arginine (R) to glutamine (Q) substitution at position 506
of the factor V protein (FV Leiden).(3,5) In general, the FV Leiden allele population carrier frequency
parallels the incidence of VTE in that population. For example, the FV Leiden allele is common among
populations of Scandinavian and European ancestry (3%-7%), where the annual VTE incidence
approaches 120 per 100,000. In contrast, the FV Leiden allele has yet to be detected in Asian or
Japanese populations, where VTE incidence is extremely low. Heterozygous FV Leiden carriers have an
8-fold risk increased for VTE, while homozygous carriers have an 80- to 100-fold increased risk. Other
genetic disorders causing deficiency of antithrombin, protein C, protein S, or hyperhomocysteinemia are
independently associated with VTE. However, interaction of these genetic disorders with the FV Leiden
allele markedly compounds the risk for VTE. Genetic and environmental (clinical) risk factors also
interact to compound the risk for VTE. The VTE risk is increased 30-fold among women who are
heterozygous FV Leiden carriers and are receiving oral contraceptives. The VTE risk during pregnancy
or the postpartum period also is increased. Homozygous FV Leiden carriers have an increased risk for
recurrent VTE, while the risk for heterozygous carriers appears to be no different than the risk for
noncarriers with VTE. Controversy exists regarding the association between the FV R506Q allele and
arterial occlusive disease (eg, coronary artery disease, myocardial infarction, stroke); more studies are
needed in order to answer this question. Direct detection of the FV Leiden gene mutation can be
performed on patient blood leukocyte genomic DNA. See The Diagnosis and Treatment of
Hypercoagulability States, Mayo Medical Laboratories Communique 2001 Nov;26(11) for more
information regarding diagnostic strategy.
Useful For: Direct mutation analysis should be reserved for patients with clinically suspected
thrombophilia and: -Activated protein C (APC)-resistance proven or suspected by a low APC-resistance
ratio -Family history of the factor V (FV Leiden) mutation It may be appropriate to screen those women
contemplating oral contraceptive use or pregnancy, with consideration of an alternative form of
contraceptive therapy or venous thromboembolism (VTE) prophylaxis during pregnancy or the
postpartum state for women with FV Leiden allele Knowledge of the FV Leiden allele status may alter
Current as of January 3, 2013 2:22 pm CST 800-533-1710 or 507-266-5700 or MayoMedicalLaboratories.com Page 711