Biochemistry
| Synonym | Antihaemophilic Globulin B, Christmas-Factor |
|---|---|
| Molecular weight | 55.400 Da |
| Synthesis | Liver |
| Half-life | 18 - 30 hours |
| Plasma concentration | 3 - 5 µg/ml |
| Normal range | 70 - 130% |
The vitamin K-dependent factor IX is activated by factor XIa from the intrinsic system and by the tissue factor/factor VIIa-complex of the extrinsic system (Josso-loop). Factor IXa with factor VIII as cofactor, phospholipids and calcium ions forms the tenase-complex on which the activation of factor X takes place.
Clinical significance
Hereditary factor IX deficiency is passed on X-chromosomally recessive and is defined as haemophilia B. Its course and symptoms are comparable to those of haemophilia A. However, the course of the disease, in which spontaneous bleeding may occur, is somewhat milder. An acquired factor IX-deficiency occurs as a result of vitamin K-deficiency, liver disease, asparaginase therapy and DIC. In substitution therapy formation of inhibitors against factor IX can be observed in 2-4% of the patients.
Indication
- Suspected haemophilia B
- Monitoring of substitution therapy in haemophilia B
- Suspected inhibitor formation against factor IX
- Factor IX determination in factor IX-concentrates
Literature
- Limentani SA et al. The biochemistry of factor IX. In: Hemostasis and thrombosis. Basic principles and clinical practice, 3rd edition. Colman RW, Hirsh J, Marder VJ, Salzman EW (eds.) Lippincott, Philadelphia 94, 1994.
- Andersson CO et al. Purification and characterization of human factor IX. Thromb Res 7, 451-459, 1975.
- Tans G et al. Activation of factor IX by factor XIa - A spectrophotometric assay for factor IX in human plasma. Thromb Haemost 48(2), 127-132, 1982.
- Van Hylckama A et al. High levels of factor IX increase the risk of venous thrombosis. Blood 95, 3678-3682, 2000.
- Moola Z et al. Measurement of activated factor IX in a high purity factor IX concentrate (Replenine ® ). Thromb Haemost (Suppl) 92, 1999.
- Pickering WM, Gray E. The effect of activated Factor IX on the Factor IX coagulant and NAPTT activity of high-purity factor IX concentrates. J Thromb Haemost 5 Supplement 2, P-T-156, 2007.
- Mahdi AJ, Obaji SG, Collins PW. Role of enhanced half-life factor VIII and IX in the treatment of haemophilia. Br J Haematol. Jun 169(6), 768-76, 2015.
- Bowyer AE, Duncan EM, Antovic JP. Role of chromogenic assays in haemophilia A and B diagnosis. Haemophilia. May 29, 2018.