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Coagulation Factors

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Also known as: Factor Assays; Blood Clotting Factors; Clotting Factors [or by the individual factor number (Factor I, Factor II, etc.) or name (Fibrinogen, Prothrombin, etc.)]
Formal name: [see table]

At a Glance

Why Get Tested?

To determine whether levels of one or more of your coagulation factors are increased, normal, or decreased

When to Get Tested?

When you have unexplained or prolonged bleeding, an abnormal Prothrombin Time (PT) or Partial Thromboplastin Time (PTT) test, or have a relative with a hereditary coagulation factor deficiency; you may be tested when your doctor wants to monitor the severity of a factor deficiency and/or the effectiveness of treatment.

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None

The Test Sample

What is being tested?

Coagulation factor tests measure the function of proteins essential for blood clot formation. Each test evaluates one of several coagulation factors produced by the liver. When someone has an unexplained bleeding episode, one possible cause is a reduction in the level of a coagulation factor in their blood. Measuring these factors can help a doctor determine the cause of the bleeding and the best treatment. 

The adequacy of a coagulation factor is typically determined by measuring the activity of the factor in blood. Activity assays can detect reduced levels of protein or proteins that don't work properly (have reduced function). Rarely, the antigen level (quantity) of a coagulation factor may also be measured. Coagulation factor antigen tests can tell how much of the protein is present but not whether its function is normal.

When an injury occurs that results in bleeding, the coagulation system is activated and plugs the hole in the leaking blood vessel with a clot while still keeping blood flowing through the vessel by preventing the clot from getting too large. The coagulation system consists of a series of proteins (coagulation factors) that activate in a step-by-step process called the coagulation cascade. The end result is the formation of insoluble fibrin threads that link together at the site of injury, along with aggregated cell fragments called platelets to form a stable blood clot. The clot prevents additional blood loss and remains in place until the injured area has healed. Blood clotting is dynamic; once a clot is formed, other factors are activated that slow clotting or dissolve the clot in a process called fibrinolysis. The clot is eventually removed as the injury site is healed. In normal healthy individuals, this balance between clot formation and removal ensures that bleeding does not become excessive and that clots are removed once they are no longer needed.

  There are nine coagulation factor proteins that are routinely measured clinically (see table below). These factors are referred to by a name or Roman numeral or both in some cases. For example, coagulation factor II is also known as prothrombin. When one or more of these factors are produced in too small a quantity, or are not functioning correctly, they can cause excessive bleeding.

coagulation factor other common name
I Fibrinogen
II Prothrombin
III Tissue factor
V  
VII  
VIII Antihemophilic factor A
IX

Antihemophilic factor B

(Christmas factor)

X Stuart-Prower factor
XI  
XIII Fibrin stabilizing factor

How is the sample collected for testing?

A blood sample is drawn from a vein in the arm.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

Common Questions

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Article Sources

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Sources Used in Current Review

Pagana, K. D. & Pagana, T. J. (© 2011). Mosby's Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pp 272–278.

(© 1995-2012). Test ID: F8A Coagulation Factor VIII Activity Assay, Plasma. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/9070 through http://www.mayomedicallaboratories.com. Accessed May 2012.

Dugdale, D. (2011 February 28). Factor VII assay. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003676.htm. Accessed May 2012.

Schwartz, R. et. al. (Updated 2011 February 2). Factor II. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/209742-overview#showall through http://emedicine.medscape.com. Accessed May 2012.

Ramanarayanan, J. et. al. (Updated 2011 May 19). Factor VII. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/209585-overview through http://emedicine.medscape.com. Accessed May 2012.

Devkota, B. (Updated 2012 April 16). Factor II, Prothrombin. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/2085225-overview#showall through http://emedicine.medscape.com. Accessed May 2012.

Spence, R. et. al. (2010 January 12). Hemostatic Disorders, Nonplatelet. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/210467-overview through http://emedicine.medscape.com. Accessed May 2012.

Clarke, W., Editor (© 2011). Contemporary Practice in Clinical Chemistry 2nd Edition: AACC Press, Washington, DC. Pp 265-272.

Sources Used in Previous Reviews

Pagana, Kathleen D. & Pagana, Timothy J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 275-280.

Thomas, Clayton L., Editor (1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].

Clarke, W. and Dufour, D. R., Editors (2006). Contemporary Practice in Clinical Chemistry, AACC Press, Washington, DC. Harris, N. et. al. Chapter 19: Assessment of Hemostasis in the Clinical Laboratory pp 227-239.

Moake, J. (2006 May, Revised). Blood Disorders, Bleeding and Clotting Disorders, Introduction. Merck Manual Home Edition [On-line information]. Available online through http://www.merck.com. Accessed on 3/14/07.

McPherson R, Pincus M, eds, (2007). Henry's Clinical Diagnosis and Management by Laboratory Methods, 21st edition, Saunders Elsevier.

Colman RW, Marder VJ, Clowes AW, George JN, Goldhaber SZ, eds, (2006). Hemostasis and Thrombosis, Basic Principles and Clinical Practice. 5th edition, Lippincott Williams and Wilkins.

Thomas, Clayton L., Editor (1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].

Van Cott, E. and Laposata, M (2002 November 19, Revised). Coagulation Factor Assays. Mass Gen Hosp Handbook [On-line information]. Available online through http://www.mgh.harvard.edu.

Vitamin K Deficiency. The Merck Manual of Diagnosis and Therapy, Section 1. Nutritional Disorders, Chapter 3. Vitamin Deficiency, Dependency, And Toxicity [On-line information]. Available online through http://www.merck.com.

(2003 March 25). Vitamin K. The Linus Pauling Institute's Micronutrient Information Center [On-line information]. Available online through http://lpi.oregonstate.edu.

DeLoughery, T. (1999 March 15). Tests of Hemostasis and Thrombosis. OHSU [Online student handout]. Available online through http://www.ohsu.edu.

Elstrom, R. (2001 October 21, Updated). Bleeding disorders. MEDLINEplus Health Information, Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/001304.htm.

Elstrom, R. (2001 November 10, Updated). Factor XII assay. MEDLINEplus Health Information, Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003681.htm.

Elstrom, R. (2001 October 14, Updated). Factor XII (Hageman factor) deficiency. MEDLINEplus Health Information, Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000545.htm.

Elstrom, R. (2001 October 14, Updated). Factor X deficiency. MEDLINEplus Health Information, Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000553.htm.

Elstrom, R. (2001 October 9, Updated). Factor VIII assay. MEDLINEplus Health Information, Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003678.htm.

Elstrom, R. (2001 November 10, Updated). Factor IX assay. MEDLINEplus Health Information, Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003679.htm.

Elstrom, R. (2001 November 10, Updated). Factor V assay. MEDLINEplus Health Information, Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003675.htm.

Elstrom, R. (2002 May 6, Updated). Factor V deficiency. MEDLINEplus Health Information, Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000550.htm.

Elstrom, R. (2001 October 6, Updated). Hemophilia B. MEDLINEplus Health Information, Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000539.htm.

Elstrom, R. (2001 November 10, Updated). Factor II deficiency. MEDLINEplus Health Information, Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000549.htm.

Elstrom, R. (2001 November 10, Updated). Factor II assay. MEDLINEplus Health Information, Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003674.htm.

Elstrom, R. (2001 November 10, Updated). Factor X assay. MEDLINEplus Health Information, Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003680.htm.

Elstrom, R. (2001 November 25, Updated). PT. MEDLINEplus Health Information, Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003652.htm.

Elstrom, R. (2001 November 25, Updated). PTT. MEDLINEplus Health Information, Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003653.htm.

Elstrom, R. (2001 November 10, Updated). Factor VII assay. MEDLINEplus Health Information, Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003676.htm.

Elstrom, R. (2001 October 14, Updated). Factor VII deficiency. MEDLINEplus Health Information, Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000548.htm.

What is a Bleeding Disorder?, History. National Hemophilia Foundation, Bleeding Disorders Info Center [On-line information]. Available online through http://www.hemophilia.org.

What is a Bleeding Disorder? National Hemophilia Foundation, Bleeding Disorders Info Center [On-line information]. Available online through http://www.hemophilia.org.

Hemophilia A (Factor VIII Deficiency). National Hemophilia Foundation, Bleeding Disorders Info Center [On-line information]. Available online through http://www.hemophilia.org.

Menta, S. (1999 Spring). The Coagulation Cascade. Physiology Disorders Evaluation, College of Medicine, University of Florida [On-line information]. Available online through http://www.medinfo.ufl.edu.

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