title: Why factor XI deficiency is a clinical concern.
abstract: BACKGROUND
  Inherited fXI deficiency has been an enigma since its discovery in 1953. The variable and relatively mild symptoms in patients with even the most severe form of the disorder seem out of step with the marked abnormalities in standard clotting assays. Indeed, the contribution of factor XI to hemostasis in an individual is not adequately assessed by techniques available in modern clinical laboratories.
  
  
  METHODS
  We discuss clinical studies, genetic/genomic analyses, and advances in laboratory medicine that are reshaping our views on the role of factor XI in pathologic coagulation. We review how the disorder associated with factor XI deficiency has contributed to changes in blood coagulation models, and discuss the complex genetics of the deficiency state and its relationship to bleeding. Finally, we cover new laboratory approaches that may distinguish deficient patients who are prone to bleeding from those without such predisposition. Expert commentary: Advances in understanding the biology of factor XI have led to modifications in treatment of factor XI-deficient patients. Factor replacement is used more judiciously, and alternative approaches are gaining favor. In the future, better laboratory tests may allow us to target therapy to those patients who would benefit most.
authors.affiliation: a Department of Pathology, Microbiology and Immunology , Vanderbilt University , Nashville , TN , USA.|b The Department of Pediatrics , Vanderbilt University , Nashville , TN , USA.
authors.forename: Allison P
authors.initials: AP
authors.lastname: Wheeler
authors.affiliation: a Department of Pathology, Microbiology and Immunology , Vanderbilt University , Nashville , TN , USA.|c The Department of Medicine , Vanderbilt University , Nashville , TN , USA.
authors.forename: David
authors.initials: D
authors.lastname: Gailani
mesh_terms: D001777:Blood Coagulation; D001780:Blood Coagulation Tests; D005172:Factor XI / Q000235:genetics / Q000378:metabolism; D005173:Factor XI Deficiency / Q000097:blood* / Q000150:complications / Q000175:diagnosis / Q000209:etiology*; D056726:Genetic Association Studies; D006470:Hemorrhage / Q000209:etiology; D006801:Humans; D010641:Phenotype
chemical_list: D005172:Factor XI
keywords: Factor XI; contact activation; factor XI deficiency; factor XII; prekallikrein