Factor XI Activity Test

Factor XI activity testing is a functional (coagulation) test that measures the functional activity of coagulation factor XI (Factor Eleven) in blood plasma, expressed as a percentage of normal activity. Factor XI is a protein that plays a role in the intrinsic pathway of blood clotting. It is used to diagnose hereditary factor XI deficiency (also known as hemophilia C), a bleeding disorder inherited in an autosomal recessive pattern, affecting males and females equally.