Coagulation Factor IX Activity Assay, Plasma
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Factor IX is a vitamin K-dependent serine protease synthesized in the liver and participates in the intrinsic coagulation pathway. Its biological half-life is 18 to 24 hours.
Congenital deficiency inherited as an X-linked recessive bleeding disorder (hemophilia B). Severe deficiency (<1%) characterized by hemarthroses, deep tissue bleeding, excessive bleeding with trauma and ecchymoses.
Acquired deficiency associated with liver disease, vitamin K deficiency, warfarin therapy and inhibitors (rare).
Diagnosing deficiencies, particularly hemophilia B (Christmas disease)
Assessing the impact of liver disease on hemostasis
Investigation of a prolonged activated partial thromboplastin time
Acquired deficiency is more common than congenital.
Mild hemophilia B: 5% to 50%
Moderate hemophilia B: 1% to 5%
Severe hemophilia B: <1%
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Liver disease, warfarin therapy, or vitamin K deficiency may lower factor IX levels.
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.
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.
Clinical References Provides recommendations for further in-depth reading of a clinical nature
1. Barrowcliffe TW, Raut S, Sands D, Hubbard AR: Coagulation and chromogenic assays of factor VIII activity: general aspects, standardization, and recommendations. Semin Thromb Hemost 2002 Jun;28(3):247-256
2. Franchini M, Lippi G, Favaloro EJ: Acquired inhibitors of coagulation factors: part II. Semin Thromb Hemost 2012 Jul;38(5):447-453
3. Carcao MD: The diagnosis and management of congenital hemophilia. Semin Thromb Hemost 2012 Oct;38(7):727-734