Factor VIII Activity Blood Test

Factor VIII Activity Blood Test 

What Is a Factor VIII Activity Test and Why Is It Done?

A factor VIII (factor 8) activity blood test shows how well a protein in the blood called factor VIII is working to help blood to clot. Clotting can help prevent too much bleeding.

The test can help:

• Diagnose a blood disorder called hemophilia A. Doctors may order a factor VIII activity blood test if a child bleeds longer than normal after an injury or surgery, or has other unusual bleeding.
• Monitor the treatment of hemophilia A.
• Find the reason for an abnormal (unusual) result on other blood clotting tests, like partial thromboplastin time (PTT).
• Check for a bleeding disorder called von Willebrand disease, along with other tests.

What Is Factor VIII?

Factor VIII is a kind of protein called a clotting factor. Clotting factors help blood clot properly and help prevent too much bleeding.

The body's clotting factors in blood are numbered using the Roman numerals I through XIII. They work together in a special order, almost like pieces of a puzzle. When the last piece is in place, the clot develops — but if even one piece is missing or defective (not working properly), the puzzle can't come together.

Clotting factor VIII, along with clotting factor IX, is involved in the creation of a "net" that closes a torn blood vessel. An abnormal gene can make some kids not have enough factor VIII, causing the bleeding disorder known as hemophilia A. Not having enough factor IX is known as hemophilia B.

Top Things to Know

• The factor VIII (factor 8) activity blood test measures the level of a protein in the blood called factor VIII.
• The test can help check for bleeding disorders like hemophilia A or von Willebrand disease.
• Kids might need to stop taking certain medicines or not eat or drink before the blood test.
• Your doctor can explain what it means if the level of factor VIII activity is low or high.

How Can I Help My Child Prepare for a Blood Test?

To help kids get ready for a blood test, find out if they need to fast (not eat or drink) or should stop taking medicines before the test. Explain what to expect during the test.

If your child is nervous about it, work together on ways to stay calm. Deep breathing or even imagining being in a place that makes your child feel safe and relaxed can help.

What Do Factor VIII Activity Test Results Mean?

Your doctor will explain what the results of the factor VIII activity test mean for your child. What’s “normal” varies based on things like age and gender.

Low Factor VIII Activity

With a low level of factor VIII activity, the factor VIII protein isn’t working well, so blood isn’t clotting as it should. This could be due to things like hemophilia A, von Willebrand disease, or another blood disorder.

High Factor VIII Activity

With a high level of factor VIII activity, the factor VIII protein is working too hard, so blood is clotting too much. This may cause blood clots in places like veins, which could be serious. Things like inflammation, a liver problem, diabetes, pregnancy, or obesity could increase factor VIII activity.

What Else Should I Know?

If you have questions about the factor VIII activity test, other blood clotting tests, or what the results mean, talk to your doctor.