Factor VII assay
What is Factor VII Assay?
A factor VII assay is a type of blood test used to measure the activity of factor VII. Factor VII is one of the clotting factors that is needed for blood clotting. When the body experiences bleeding, factor VII helps to stop the bleeding by promoting the formation of a clot. The activity of factor VII can be used to diagnose a variety of bleeding and clotting disorders, such as hemophilia, von Willebrand disease, and thrombophilia.
Preparation for Factor VII Assay
A factor VII assay requires a sample of blood. In most cases, a vein in your arm will be used to take a sample. The area will be cleaned and a tourniquet will be wrapped around your arm, causing the veins to become more prominent. The health care specialist will insert a needle into your vein and collect the blood in a vial.
Procedure for Factor VII Assay
Once the blood has been collected, it will be processed in order to measure the activity of factor VII. This typically involves looking at the level of enzyme activity present in the sample. A laboratory technician will then assess the results to determine the level of activity, which can then be used to diagnose a variety of conditions.
Types of Factor VII Assay
- One-stage method: This is a direct method which involves the addition of calcium ions to the sample. It will measure the activity of factors VII, IX, and X.
- Two-stage method: This uses two steps to measure the activity of factors VII, IX, and X. The first step is an activation factor assay which uses thromboplastin and calcium ions. The second step is a clotting time assay.
- Chromogenic method: This method uses a chromogenic substrate to measure the activity of factor VII. It is more precise and reliable than the one-stage and two-stage methods.
Risks of Factor VII Assay
A factor VII assay is a very safe procedure and does not pose any significant risks. As with any procedure involving a needle, there is a small risk of infection at the area where the needle is inserted. However, this risk is extremely low.
Why is a Factor VII Assay Used?
A factor VII assay is typically used to diagnose a variety of bleeding and clotting disorders. These disorders can cause a variety of symptoms, such as excessive bleeding after an injury, frequent nosebleeds, or easy bruising. A factor VII assay can detect if the activity of this factor is low, which can help to diagnose these disorders. Additionally, this test can also help to monitor these disorders to ensure that they are being effectively treated.
When is a Factor VII Assay Used?
A factor VII assay is typically ordered when a patient has symptoms that may be indicative of a bleeding or clotting disorder. Additionally, this test can be used to monitor the effectiveness of treatment for these disorders. It is also sometimes ordered to assess the risk of bleeding in patients who are being treated with a blood thinner, such as warfarin.