von Willebrand Factor Antigen

The von Willebrand Factor Antigen test contains 1 test with 1 biomarker.

Brief Description: The von Willebrand Factor Antigen test is a diagnostic tool that measures the quantity of von Willebrand Factor (vWF) present in a person's blood. vWF is a protein that plays a crucial role in the blood clotting process. It works by helping platelets in the blood stick together and adhere to the walls of blood vessels, which is a primary step in the clot formation process.

Also Known As: VWF Ag Test, VWF RCo Test, von Willebrand Panel Test, Ristocetin Cofactor Test

Collection Method: Blood Draw

Specimen Type: Plasma

Test Preparation: Overnight fasting is preferred

When is a von Willebrand Factor Antigen test ordered?

In order to look into a person's or their family's history of excessive or recurring bleeding episodes, VWF testing is prescribed after basic screening tests for a bleeding issue have been completed. Depending on the type of VWD a person has, different signs and symptoms may call for testing, such as:

• recurring or frequent nosebleeds
• excessive gum bleeding following dental operations
• excessive bruising following small bumps or wounds
• women who experience heavy or protracted menstrual bleeding
• blood in the feces or urine
• persistent bleeding following surgery

Even if the initial results of the VWF tests are benign, there is still a strong likelihood that VWD is present.

Further testing may be carried out to identify the person's subtype when VWF testing indicates VWD.

What does a von Willebrand Factor Antigen blood test check for?

One of the many elements of the coagulation system that cooperate and function sequentially to halt internal bleeding in the body is the protein known as von Willebrand factor. Testing for VWF quantifies the protein's blood concentration and evaluates the protein's functionality.

VWF often creates an adhesive bridge between active cell fragments called platelets and the injury site when a blood vessel is broken and bleeding starts. A stable blood clot develops as a result of the platelets aggregating at the wound site and a series of events known as activation of the coagulation cascade.

VWF also influences the availability of coagulation factor VIII, which has an impact on clotting. Factor VIII is carried by VWF in the blood, which lengthens its half-life and releases it as required. Insufficiency in functional VWF affects platelet adhesion and aggregation, factor VIII levels may drop, blood clot formation takes longer, and bleeding is hence protracted. Von Willebrand disease is a condition brought on by this deficit.

The most prevalent inherited bleeding disorder is VWD. It is a collection of disorders characterized by protracted bleeding brought on by inadequate and/or flawed VWF. There are numerous varieties and sub-categories of VWD, including:

• Type 1 - in this form of VWD, less VWF is created, but the VWF still performs as it should. Factor VIII levels are also frequently low, but they could be normal. With around 75% of cases being this kind of VWD, it is the most prevalent. It frequently results in bruising and light to moderate bleeding, such as frequent nosebleeds, heavy periods, and protracted bleeding after delivery, accidents, surgeries, and dental work. Each individual's symptoms and level of bleeding will be unique, as will each episode.
• Type 2: Although there is a normal amount of VWF in this kind, the VWF does not function normally. Bleeding could be more severe in this case. Types 2A, 2B, 2M, and 2N are subcategories of Type 2.
• Type 3 - This uncommon variety is characterized by very little factor VIII production, moderate to severe symptoms, and very low VWF production. Because of the early bleeding episodes, it is frequently found in infancy.

Rarely, VWD could be due to an acquired VWF defect, where there is no family or personal bleeding record up to the point when signs and symptoms develop.

Testing for the von Willebrand factor includes measuring the quantity of VWF with VWF antigen and assessing its functionality with VWF activity. A panel that includes all of these tests and a factor VIII activity test might be available from some labs.

Lab tests often ordered with a von Willebrand Factor Antigen test:

When a von Willebrand Factor Antigen test is ordered, it's often part of a broader evaluation of bleeding disorders. Here are some tests commonly ordered alongside it:

1. Factor VIII Activity:

   • Purpose: To measure the activity of Factor VIII, a crucial clotting factor that is carried by von Willebrand factor in the blood.
   • Why Is It Ordered: Since vWF stabilizes Factor VIII, abnormalities in vWF can lead to reduced Factor VIII activity, affecting blood clotting.

2. PT (Prothrombin Time) and aPTT (Activated Partial Thromboplastin Time):

   • Purpose: To assess the blood’s ability to clot by measuring different pathways of the coagulation cascade.
   • Why Is It Ordered: To evaluate overall blood clotting function and identify abnormalities in the coagulation pathway.

3. Complete Blood Count (CBC) with Platelet Count:

   • Purpose: To evaluate overall blood health, including the number and quality of red blood cells, white blood cells, and platelets.
   • Why Is It Ordered: To check for other causes of bleeding or clotting disorders, such as thrombocytopenia (low platelet count).

4. Blood Group Typing:

   • Purpose: To determine the blood group.
   • Why Is It Ordered: Certain blood types (like Type O) can have naturally lower levels of von Willebrand factor.

These tests, when ordered alongside a von Willebrand Factor Antigen test, provide a comprehensive evaluation of bleeding disorders, particularly von Willebrand disease. They help in diagnosing the condition, determining its type and severity, and guiding appropriate treatment. The specific combination of tests will depend on the individual’s symptoms, bleeding history, and family history.

Conditions where a von Willebrand Factor Antigen test is recommended:

The primary condition associated with the von Willebrand Factor Antigen test is von Willebrand Disease (vWD), which is the most common inherited bleeding disorder. vWD is characterized by either a deficiency in or a dysfunction of the vWF protein. Additionally, some cases of acquired (not inherited) bleeding disorders might also present with reduced vWF levels.

How does my health care provider use a von Willebrand Factor Antigen test?

A personal or familial history of excessive bleeding, as well as excessive or repeated bleeding events, are investigated with the Von Willebrand factor test. Testing is used to identify the different kinds of von Willebrand disease and aid in the diagnosis of the condition.

VWF is a protein that functions as one of numerous elements of the coagulation system to halt bleeding and create a durable blood clot. Bleeding could be considerable or last a long time if VWF is not present in sufficient amounts or is not functioning effectively. The most prevalent inherited bleeding disorder is known as von Willebrand disease. Type 1, Type 2, and Type 3 are the several types of VWD. The most prevalent form, type 1, is also the mildest of the three. Occasionally, an acquired VWF deficit may be the cause of VWD.

There are two possible exam types:

• The VWF antigen test detects the concentration of the VWF protein in the blood; the VWF activity test evaluates the protein's efficiency.
• In addition to other tests for bleeding disorders such a complete blood count, platelet count, platelet function tests, PT, and/or PTT, these tests may also be ordered in conjunction with a coagulation factor VIII activity test.

What do my von Willebrand Factor Antigen test results mean?

It can be difficult to interpret VWF test findings and may be necessary to consult a physician with expertise in bleeding problems, such as a hematologist or coagulation specialist, particularly when identifying subtypes. Test results for VWF antigen and VWF activity may be normal in people with mild VWD and considerably lowered in people without VWD.

A considerably reduced VWF antigen test in a patient with normal or almost normal bleeding disorder screening test results indicates that the patient has a quantitative VWF deficiency and may have Type 1 VWD or, less frequently, acquired VWD.

The person may have Type 2 VWD if the VWF antigen test results are normal or nearly normal and the VWF activity is lowered. To identify the subtype that is present, more testing will be necessary.

If little or no VWF and factor VIII are present, then the person may have Type 3 VWD. This is usually observed in young children who have bleeding episodes. It might seem to be caused by hemophilia A, a male-specific bleeding condition caused by a factor VIII deficiency.

High VWF antigen levels and VWF activity are not regarded as diagnostic. One of the many acute phase reactants is VWF. This implies that levels will transiently rise in response to trauma, infections, inflammation, and inflammatory processes. Moreover, they rise during pregnancy and when estrogen-related drugs like oral contraceptives are used.

Most Common Questions About the von Willebrand Factor Antigen test:

Purpose and Indications for the von Willebrand Factor Antigen Test

Why is the von Willebrand Factor Antigen test performed?

The von Willebrand Factor Antigen test is primarily administered to diagnose von Willebrand's Disease (VWD) – the most common inherited bleeding disorder. The test measures the amount of von Willebrand factor (VWF) – a protein necessary for blood clotting – in a patient's blood.

Can the von Willebrand Factor Antigen test help in distinguishing between types of von Willebrand's Disease?

Yes, the test can aid in classifying the different types of VWD. Depending on the VWF levels and the activity of VWF in the blood, a clinician can discern between Type 1, Type 2, and Type 3 VWD.

Interpreting the Results

What do the results of the von Willebrand Factor Antigen test indicate?

The levels of VWF in the blood determine the test results. If VWF levels are lower than the reference range, it might indicate VWD or another clotting disorder. However, elevated VWF levels can sometimes be seen in conditions like stress, pregnancy, or certain diseases.

If the von Willebrand Factor Antigen test is normal, does that eliminate the possibility of having VWD?

Not always. A person might still have Type 2 VWD because this type sometimes presents with normal VWF levels but the VWF doesn't function properly. Additional tests that measure VWF activity may be required.

Follow-up and Treatment

After getting the results of the von Willebrand Factor Antigen test, what should be the next steps?

If VWD is confirmed or suspected based on the test results, a consultation with a hematologist or a bleeding disorder specialist is essential. They will provide a comprehensive assessment, recommend further tests if necessary, and guide treatment options.

How do the results of the von Willebrand Factor Antigen test influence treatment options?

Treatment for VWD depends on its type and severity. If the test identifies low VWF levels, treatments might include desmopressin or VWF concentrates to boost these levels. Knowing the exact VWF level and its functionality is pivotal in tailoring the appropriate therapeutic approach.

Disease Monitoring and Complications

Should the von Willebrand Factor Antigen test be repeated periodically?

For individuals diagnosed with VWD, periodic testing might be recommended to monitor the disease, especially before surgeries or dental procedures. For those with a family history of VWD but no symptoms, periodic testing might be performed as a precautionary measure.

Can the von Willebrand Factor Antigen test predict complications or disease progression?

While the test provides insights into VWF levels, it doesn't directly predict complications. However, severely low VWF levels might indicate a higher risk for bleeding events. Monitoring these levels and understanding their implications helps in managing potential complications.

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.