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Factor XII (Hagemann)
Last reviewed: 23.04.2024
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The reference values (norm) of activity of factor XII in blood plasma are 65-150%.
Factor XII (Hagemann) is a sialoglycoprotein activated by collagen, contact with a foreign surface, adrenaline and a number of proteolytic enzymes (in particular, plasmin). Factor XII initiates intravascular coagulation, in addition, factor XIIa transforms prekallikrein plasma into kallikreins. Active factor XII serves as an activator of fibrinolysis.
With the deficiency of factor XII, the time of blood coagulation and APTT was increased without signs of bleeding. In clinical practice, the determination of factor XII activity is used mainly to detect its congenital deficiency. Deficiency of factor XII should be suspected with a significant lengthening of clotting time and APTT. In most cases, the Hageman defect is inherited by an autosomal recessive type. Between the degree of clotting disorder and the deficiency of factor XII, there is a strict correspondence: with pronounced hypocoagulation, the level of activity of this factor in plasma does not exceed 2% and more often below 1%; with a moderate violation of clotting, it varies from 3 to 9%. If the activity of factor XII in plasma is 10% or more, then the blood clotting time, APTT and other tests are normal.
Acquired deficiency of factor XII characterizes coagulopathy of consumption due to ICE.
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