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von Willebrand Factor

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Also known as: VWF:Ag; VWF:RCo; von Willebrand Panel; Ristocetin Cofactor
Formal name: von Willebrand Factor Antigen and von Willebrand Factor Activity

At a Glance

Why Get Tested?

To help determine the cause of unexplained excessive or repeated episodes of bleeding, to diagnose von Willebrand disease (VWD), and to distinguish between different types of VWD

When to Get Tested?

When you have a personal or family history of heavy, prolonged, and/or spontaneous bleeding; when your health care provider suspects that you may have a bleeding disorder

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None

The Test Sample

What is being tested?

Von Willebrand factor (vWF or VWF) is a protein that is one of several components of the coagulation system that work together, and in sequence, to stop bleeding within the body. VWF testing measures the amount of the protein present in blood and determines how well the protein functions.

Normally, when a blood vessel is damaged and bleeding begins, VWF forms an adhesive bridge between activated cell fragments called platelets and the injury site. This is followed by the clumping (aggregation) of platelets at the site and a series of actions referred to as activation of the coagulation cascade, resulting in the formation of a stable blood clot.

VWF further affects clotting by influencing the availability of coagulation factor VIII. VWF carries factor VIII in the blood, increases its half-life, and releases it as necessary. If the amount of functional VWF is insufficient, then platelet adherence and aggregation are affected, levels of factor VIII could be decreased, blood clot formation takes longer, and therefore bleeding is prolonged. This deficiency causes a condition referred to as von Willebrand disease (VWD).

VWD is the most common inherited bleeding disorder. It is a group of conditions associated with prolonged bleeding due to deficient and/or defective VWF. VWD is separated into different types and sub-types, including:

  • Type 1 – with this type of VWD, there is a decrease in the amount of VWF produced, but the VWF functions normally. Levels of factor VIII are also typically low but may be normal. This is the most common type of VWD, accounting for about 75% of cases. It tends to cause bruising and mild to moderate bleeding, such as persistent nosebleeds, heavy menstrual periods, and prolonged bleeding following childbirth, trauma, dental procedures, and surgeries. Symptoms and the severity of bleeding will vary from person to person and from episode to episode.
  • Type 2 – this type is associated with a normal amount of VWF, but the VWF does not function normally. Bleeding may be more severe with this with this type. Type 2 is further divided into Types 2A, 2B, 2M, and 2N.
  • Type 3 – this rare type is associated with very little VWF production, very low factor VIII levels, and moderate to severe symptoms. It is often detected in infancy because of early bleeding episodes.

Rarely, VWD may be due to an acquired VWF deficiency, where there is no family or personal bleeding history up to the point when signs and symptoms develop. (For more on this, see Common Questions #7.)

Von Willebrand factor testing includes VWF antigen, which measures the amount of VWF, and VWF activity (also known as Ristocetin Cofactor), which evaluates the function of VWF. Some laboratories may offer a panel that includes both of these tests along with a factor VIII activity test.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into 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

Pollak, E. (Updated 2012 April 6) von Willebrand Disease. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/206996-overview through http://emedicine.medscape.com. Accessed November 2013.

Medscape Editorial Staff (Updated 2012 October 1). von Willebrand Factor Antigen (Factor VIII:R Antigen) Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/2086366-overview through http://emedicine.medscape.com. Accessed November 2013.

(2011 June 1). What Is von Willebrand Disease? National Heart Lung and Blood Institute [On-line information]. Available online at http://www.nhlbi.nih.gov/health/health-topics/topics/vwd/ through http://www.nhlbi.nih.gov. Accessed November 2013.

Heikal, N. et. al. (Updated 2013 October). von Willebrand Disease – VWD. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/VWD.html through http://www.arupconsult.com. Accessed November 2013.

Gersten, T. (Updated 2012 February 16). Von Willebrand disease. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000544.htm. Accessed November 2013.

(© 1995–2013). von Willebrand Profile. Mayo Clinic Mayo Medical Laboratory [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/83099 through http://www.mayomedicallaboratories.com. Accessed November 2013.

Pagana, K. D. & Pagana, T. J. (© 2011). Mosby's Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pp 277.

Clarke, W., Editor (© 2011). Contemporary Practice in Clinical Chemistry 2nd Edition: AACC Press, Washington, DC. Pp 277-279.

McPherson, R. and Pincus, M. (© 2011). Henry's Clinical Diagnosis and Management by Laboratory Methods 22nd Edition: Elsevier Saunders, Philadelphia, PA. Pp 816-819.

(Updated 1, 2011) National Heart Lung and Blood Institute. What is von Willebrand Disease? Available online at http://www.nhlbi.nih.gov/health/health-topics/topics/vwd/ through http://www.nhlbi.nih.gov. Accessed November 2013.

Sources Used in Previous Reviews

Yawn, B. et. al.(2009 December 1) Diagnosis and Management of Von Willebrand Disease: Guidelines for Primary Care. American Family Physician [On-line information]. Available online at http://www.aafp.org/afp/2009/1201/p1261.html through http://www.aafp.org. Accessed February 2010.

Pagana, K. D. & Pagana, T. J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 280.

Wu, A. (© 2006). Tietz Clinical Guide to Laboratory Tests, 4th Edition: Saunders Elsevier, St. Louis, MO. Pp 1144-1145.

Rodgers, III, G. and Smock, K. (Updated 2009 August). von Willebrand Disease – vWD. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/vWD.html?client_ID=LTD through http://www.arupconsult.com. Accessed February 2010.

(Revised 2009 May). What Is von Willebrand Disease? National Heart Lung and Blood Institute [On-line information]. Available online at http://www.nhlbi.nih.gov/health/dci/Diseases/vWD/vWD_WhatIs.html through http://www.nhlbi.nih.gov. Accessed February 2010.

Geil, J. (Updated 2009 May 21). Von Willebrand Disease. eMedicine [On-line information]. Available online at http://emedicine.medscape.com/article/959825-overview through http://emedicine.medscape.com. Accessed February 2010.

Goodeve, A. and James, P. (2009 June 4). von Willebrand Disease. GeneReviews [On-line information]. Available online at http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene∂=von-willebrand through http://www.ncbi.nlm.nih.gov. Accessed February 2010.

Mayo Clinic Staff (2009 February 7). Von Willebrand disease. MayoClinic.com [On-line information]. Available online at http://www.mayoclinic.com/health/von-willebrand-disease/DS00903 through http://www.mayoclinic.com. Accessed February 2010.

George, J. (Revised 2009 May). Von Willebrand's Disease. Merck Manual for Healthcare Professionals [On-line information]. Available online at http://www.merck.com/mmpe/sec11/ch133/ch133h.html#sec11-ch133-ch133h-410 through http://www.merck.com. Accessed February 2010.

Grund, S. (Updated 2008 March 21). Von Willebrand disease. MedlinePlus Medical Encylopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000544.htm. Accessed February 2010.

Link, R. (Updated 2009 March 4). Bleeding Disorders, Frequently Asked Questions. Womenshealth.gov [On-line information]. Available online at http://www.womenshealth.gov/faq/bleeding-disorders.cfm through http://www.womenshealth.gov. Accessed February 2010.

Clarke, W. and Dufour, D. R., Editors (© 2006). Contemporary Practice in Clinical Chemistry: AACC Press, Washington, DC. Pp 236-237.

Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. McPherson R, Pincus M, eds. Philadelphia, PA: Saunders Elsevier: 2007 pp 760-762.

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