Coagulation factor IX

• The material for testing is blood.
• The patient must not be undergoing treatment with high molecular weight heparin.
• The patient does not need to fast.

Samples brought from outside are not accepted for testing.

Coagulation factor IX (FIX, Christmas factor, antihemophilic factor B)
FIX is a vitamin K-dependent glycoprotein. It is activated by VIIa/TF or XIa. Once activated, factor IXa activates factor X in the presence of factor VIIIa, platelet phospholipids, and calcium ions. FVIIIa is an essential cofactor for factor IXa. Therefore, deficiency of either factor has a similar clinical picture. FIX deficiency is associated with hemophilia B. Laboratory tests in most cases of hemophilia B show a prolonged APTT with a normal INR. Factor IX measurement is necessary to establish the diagnosis.
Reduced FIX activity occurs in:
• Congenital factor IX deficiency (hemophilia B)
• Treatment with vitamin K antagonists
• Significant liver damage
• Amyloidosis
• Treatment with valproic acid
• Vitamin K deficiency
• Acquired FIX deficiency (rarely in cancer and autoimmune diseases, after surgery)

Increased FIX activity occurs in:
• Diabetes
• Corticosteroid therapy
Increased FIX activity is associated with an increased risk of cardiovascular events. Determination of this protein is recommended in the diagnosis of venous thrombosis of unknown cause.

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