F_9 - Clinical: Coagulation Factor IX Activity Assay, Plasma

Test Catalog

Test Name

Test ID: F_9    
Coagulation Factor IX Activity Assay, Plasma

Useful For Suggests clinical disorders or settings where the test may be helpful

Diagnosing deficiencies, particularly hemophilia B (Christmas disease)


Assessing the impact of liver disease on hemostasis


Investigation of a prolonged activated partial thromboplastin time

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

See Hemophilia Testing Algorithm in Special Instructions.

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).

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.

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.

Interpretation Provides information to assist in interpretation of the test results

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.

Clinical Reference Recommendations for 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

Special Instructions and Forms Library of PDFs including pertinent information and consent forms, specimen collection and preparation information, test algorithms, and other information pertinent to test