Factor V Quick Facts
- Synthesis: Liver, megakaryocytes, endothelial cells
- Molecular mass: 350 000 D
- Half-life: 12 – 15 hours
- Plasma concentration: 4 – 14mg/l
- Normal range: 60 – 120% or 0.6 – 1.2U/ml
Biochemistry of Factor V
As cofactor in the prothrombinase complex, the activated form of factor V (accelerin) accelerates the activation of prothrombin to thrombin by factor Xa. The activation of factor V to factor Va can be effected by thrombin, factor Xa and certain snake venoms such as the Russell’s Viper Venom (RVV). Apart from the procoagulant effect of factor Va, factor V is involved as a cofactor together with protein S in the anticoagulant activity of activated protein C (APC).
Clinical significance of Factor V
A homozygous hereditary factor V deficiency is very rare, whereas the heterozygous form is often observed. Apart from a true deficiency also altered factor V molecules (dysfunctional forms) exist. An acquired factor V deficiency occurs as a result of hepatic disease, DIC, hyperfibrinolytic conditions and chronic myeloid leukemia. Increased factor Va concentrations as a result of thrombin activation can be observed during phase I of DIC, in acute thrombosis, in postoperative phases and after inflammation.
Clinical or Research use of Factor V
- Diagnosis and monitoring of DIC
- Suspected hereditary factor V deficiency in hemorrhage of unknown cause
- Suspected factor V inhibitors
- Suspected pseudo homozygous APC Resistance due to combined FV deficiency and FV:Q506