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Test ID: F_12    
Coagulation Factor XII Activity Assay, Plasma

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Useful For Suggests clinical disorders or settings where the test may be helpful

Diagnosing deficiency of coagulation factor XII

 

Determining cause of prolonged activated partial thromboplastin time

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Factor XII is synthesized in the liver. Its biological half-life is 40 to 50 hours. Factor XII is a component of the contact activation system and is involved in both intrinsic pathway and fibrinolytic system

 

Factor XII deficiency is often discovered when activated partial thromboplastin time is found to be unexpectedly long. The deficiency causes no known bleeding disorder.

 

An association between severe factor XII deficiency and thrombosis risk has been proposed, but not proven.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Adults: 55-180%

Normal, full-term newborn infants or healthy premature infants may have decreased levels (> or =15% to 20%) which may not reach adult levels for > or =180 days postnatal.*

*See Pediatric Hemostasis References in Coagulation Studies in Special Instructions.

Interpretation Provides information to assist in interpretation of the test results

Acquired deficiency is associated with liver disease, nephritic syndrome, and chronic granulocytic leukemia.

 

Congenital homozygous deficiency: 20%

 

Congenital heterozygous deficiency: 20% to 50%

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Deficiencies of other contact activator proteins (prekallikrein, high molecular weight kininogen) can also cause prolonged activated partial thromboplastin time but do not cause clinical bleeding.

Clinical Reference Provides recommendations for further in-depth reading of a clinical nature

Renne T, Schmaier AH, Nickel KF, et al: In vivo roles of factor XII. Blood 2012 Nov 22;120(22):4296-4303

Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test