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Factor XI (antihemophilic factor C)
Last reviewed: 05.07.2025
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Reference values (norm) of factor XI activity in blood plasma are 65-135%.
Factor XI - antihemophilic factor C - glycoprotein. The active form of this factor (XIa) is formed with the participation of factors XIIa, Fletcher and Fitzgerald. Form XIa activates factor IX. With a deficiency of factor XI, the coagulogram shows an extended blood clotting time and APTT.
In clinical practice, determination of factor XI activity is used mainly for the diagnosis of hemophilia C and to differentiate between factor XI and factor XII deficiencies.
Congenital deficiency of factor XI is called Rosenthal's disease, or hemophilia C. It is an autosomal recessive hereditary disease. Bleeding is mainly observed after injuries and operations.
Acquired factor XI deficiency occurs mainly in DIC syndrome, taking anticoagulants, and intravenous administration of dextran.
The minimum hemostatic level of factor XI activity in the blood for performing operations is 15-25%; with lower activity, the risk of developing postoperative bleeding is extremely high. The minimum hemostatic level of factor XI activity in the blood for stopping bleeding is 5-15%; with lower activity, stopping bleeding without administering factor XI to the patient is impossible.
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