Factor V Assay

Written by Corinna Underwood | Published on June 8, 2012
Medically Reviewed by George Krucik, MD

What Is a Factor V Assay Test?

Each time you bleed, it triggers a series of reactions known as the coagulation cascade. Coagulation is the process your body uses to stop blood loss. Cells called platelets create a plug to cover the damaged tissue and then your body’s clotting factors interact to produce a blood clot. Low levels of clotting factors can prevent a clot from forming.

Your doctor may recommend a factor V assay test to determine if your body makes a healthy level of this particular coagulation factor. Your body needs factor V for your blood to clot normally.

What the Test Addresses

This test is used to determine if you have an adequate level of clotting factor V, one of the key factors in blood coagulation. Your doctor may recommend the test if you have a family history of bleeding disorders or if you have experienced any of the following symptoms:

  • excessive and frequent bruising or bleeding
  • frequent nose bleeds
  • frequent bleeding gums
  • bleeding within the joints and head (in newborns)
  • prolonged or heavier-than-normal menstrual periods

Severity of Symptoms

Your body produces 13 different coagulation factors that must all be present for the clotting process to proceed normally. The severity of your symptoms will depend on:

  • the type of factor deficiency you have
  • the way in which the particular factor functions
  • the amount of factor your body makes

Symptoms may also vary in different bleeding episodes. For example, you may experience excessive gum bleeding after a dental procedure on one occasion. You may have blood in your stool or urine during another episode.

You may experience few symptoms and may not become aware of a low level of coagulation factor until after a surgical procedure. However, you will have experienced excessive bleeding at an early age—perhaps even in infancy—if you have a severe factor deficiency.

Rarely, patients are deficient in both factor V and factor VIII. This condition causes much more severe episodes of bleeding. According to the National Hemophilia Foundation (NHF), combined factor V and factor VIII deficiency is a unique disorder that may be mistakenly diagnosed as a mild factor V or a mild factor VIII deficiency (NHF, 2006).

Preparing for the Test

No special preparation is necessary for this test. Tell your doctor if you are taking any blood-thinning medications, such as warfarin (Coumadin). Your doctor may advise you to stop taking blood thinners before the test.

How the Test Is Administered

Your doctor will need to take a sample of blood from your arm to perform the test. First, the site will be cleaned with an alcohol swab. Then, the doctor will insert a needle into your vein and attach a tube to the needle to collect blood. The needle will be removed and the site will be covered with a gauze pad when enough blood has been collected. The blood sample will be sent to a laboratory for analysis.

Understanding the Results

Normal Results

A normal result for a factor V assay should be between 50 and 200 percent of the laboratory reference value. Your doctor will explain the specifics of your results.

Abnormal Results

If your results are abnormal, you have a low level of factor V. This could be caused by:

  • inherited factor V deficiency, which is present at birth
  • disseminated intravascular coagulation (when the proteins that control blood clotting are over-active)

What Are the Risks of the Test?

As with any blood test, there is a slight risk of bruising, bleeding, or infection at the puncture site. In rare cases, the vein may become swollen after blood is drawn. This condition, known as phlebitis, can be treated by applying a warm compress to the site several times a day.

What to Expect After the Test

To treat factor V deficiency, you will need to replace the missing factor in your blood. Unfortunately, no factor V concentrates are currently available. The only treatment option is a transfusion of fresh, frozen blood plasma. Your doctor may also recommend the addition of platelet concentrates to help with the clotting process if you suffer from episodes of severe bleeding.

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