title: Antithrombin deficiency: issues in laboratory diagnosis.
abstract: OBJECTIVE
  To review the current understanding of the pathophysiology of antithrombin deficiency and its role in congenital thrombophilia. Recommendations for diagnostic testing of antithrombin function and concentration, derived from the medical literature and consensus opinions of recognized experts in the field, are included. These recommendations specify whom, how, and when to test.
  
  
  METHODS
  Review of the published medical literature.
  
  
  METHODS
  A summary of the medical literature and proposed testing recommendations were prepared and presented at the College of American Pathologists Conference XXXVI: Diagnostic Issues in Thrombophilia. After discussion at the conference, consensus recommendations presented in this article were accepted after a two-thirds majority vote by the participants.
  
  
  CONCLUSIONS
  Antithrombin deficiency is an infrequent genetic abnormality that may be a significant contributing cause of thrombophilia. Antithrombin deficiency also may be observed in conjunction with other genetic or acquired risk factors. Assay of antithrombin plasma levels is appropriate in the laboratory evaluation of individuals with thrombophilia, preferably using a functional, amidolytic antithrombin assay. The diagnosis of antithrombin deficiency should be established only after other acquired causes of antithrombin deficiency, such as liver disease, consumptive coagulopathy, or heparin therapy, are excluded. A low antithrombin level should be confirmed with a subsequent assay on a fresh specimen, and family studies may be helpful to establish the diagnosis. Antigenic antithrombin assays may be of benefit in subclassification of the type of antithrombin deficiency and to confirm the decreased antithrombin level in patients with type I deficiency.
authors.affiliation: Department of Clinical Pathology, Cleveland Clinic Foundation, Ohio 44195, USA. marchak@ccf.org
authors.forename: Kandice
authors.initials: K
authors.lastname: Kottke-Marchant
authors.forename: Alexander
authors.initials: A
authors.lastname: Duncan
mesh_terms: D000465:Algorithms; D000991:Antithrombins / Q000172:deficiency* / Q000502:physiology; D001780:Blood Coagulation Tests; D006801:Humans; D017410:Practice Guidelines as Topic; D015995:Prevalence; D012016:Reference Values; D012307:Risk Factors; D019851:Thrombophilia / Q000175:diagnosis* / Q000503:physiopathology
chemical_list: D000991:Antithrombins