What Is a Factor VII Assay?
Your doctor may recommend a factor VII assay to find out if your blood clots correctly. If your levels of factor VII are low, you run the risk of episodes of prolonged or excessive bleeding.
Your body needs factor VII in order to form blood clots. The factor VII assay will determine whether your body produces a healthy level of this particular coagulation factor.
The Blood Clotting Process
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 body produces 13 different coagulation factors that must all be present in order 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, and the amount of factor your body makes.
Symptoms may also vary from bleeding episode to bleeding episode. For example, on one occasion you may experience excessive gum bleeding after a dental procedure, while during another episode you may experience bloody stools.
If your level of coagulation factor is moderately low, you may experience few symptoms and may not become aware of the deficiency until after surgery or an injury. However, if you have a severe factor deficiency, you will have experienced excessive bleeding at an early age, perhaps even in infancy.
What the Test Addresses
Your doctor will order a factor assay to determine the cause of prolonged or excessive bleeding. If you have any blood clotting problems, it is important to see your doctor for a diagnosis as soon as possible. If you don’t know about your bleeding disorder beforehand, you may experience severe bleeding from emergency dental work or surgery.
Your doctor may recommend a factor VII assay if you have a family history of bleeding disorders or if you experience any of the following symptoms:
- bleeding within your joint cavities
- bleeding from your mucous membranes, such as your nostrils and gums
- bleeding within your muscles
- heavy or prolonged menstrual bleeding
- easy bruising
- frequent nosebleeds
Preparing for the Test
No special preparation is necessary for this test. You should tell your doctor if you are taking any blood-thinning medications, such as warfarin (Coumadin). Your doctor will likely advise you to stop taking blood thinners before the test.
How the Is Test Administered
To perform the test, your doctor will need to take a sample of blood from your arm. 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.
When enough blood has been collected, the needle will be removed and the site covered with a gauze pad. The blood sample will be sent to a laboratory for analysis.
Understanding Your Test Results
A normal result for a factor VII assay should be between 50 and 200 percent of the laboratory reference value. Your doctor will explain the specifics of your results.
If your results are abnormal, it means that you have a low level of factor VII. This could be caused by:
- an inherited factor VII deficiency, which is present at birth
- disseminated intravascular coagulation (a disease in which blood clotting proteins are overactive)
- liver disease, such as cirrhosis
- fat malabsorption
- a vitamin K deficiency
- the use of warfarin
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. Applying a warm compress several times a day can treat this condition, known as phlebitis.
Ongoing bleeding could be a problem if you suffer from a bleeding disorder or are taking blood-thinning medication, such as warfarin or aspirin.
What to Expect After the Test
If you are diagnosed with factor VII deficiency, your bleeding can be controlled with transfusions of fresh frozen blood plasma, factor VII concentrates, or recombinant factor VII (Novoseven). You will need to have frequent transfusions during bleeding episodes because factor VII does not remain in your body for long.
If your condition is caused by a vitamin K deficiency, you can take vitamin K supplements orally or by means of an injection under your skin.