OVERVIEW
What is blood clotting?
A natural process in the body that involves platelets & proteins known as “clotting factors”. The platelets or thrombocytes are type of blood cells that are made by the bone marrow. Whereas clotting factors are proteins made by the liver. Together they work when a blood vessel breaks (injury occurs). First platelets arrive at the area of damage and seal the leak/temporarily stop bleeding. Then clotting factors help make the clot (lump of blood to prevent bleeding) strong & stable. Clotting factors are numbered from I to XII, all working together in sequence.
What is Factor VIII level lab test?
Factor VIII and factor IX are involved in last step of clotting process and helps in creation of a net for closing the torn blood vessel. Hence, in case of clotting factor VIII deficiency due to abnormal gene, it causes hemophilia A (a bleeding disorder) in children. This lab test helps to evaluate the functioning/activity of factor VIII in blood clotting. This test is also known as antihaemophilia factor A test.
Why is Factor VIII level lab test done?
The test is done:
- As it helps find out/diagnose whether you’ve hemophilia A or another clotting disorder
- As helps in monitoring treatment of hemophilia A
- When the person shows signs and symptoms of clotting disorder like easy bruising, nosebleeds, excessive bleeding after dental procedure/mouth injury, blood in urine, & swollen/painful joints.
- As it helps identify reason behind abnormal result on other clotting tests like PTT (partial thromboplastin time) or PT (prothrombin time)
- When a child has a family member with a bleeding disorder
- Also, for evaluation of von Willebrand disease (bleeding disorder). vWF is a clotting factor to which factor VIII is attached.
- How is this test performed?
This test is performed on a blood sample. A syringe with a fine needle is used to withdraw blood from a blood vessel in your arm. The healthcare provider will tie an elastic band around your arm to make the blood vessels swell with blood. This makes it easier to withdraw blood. You may be asked to tightly clench your fist. Once the veins are clearly visible, the area is cleaned with an antiseptic solution and then the needle is inserted into the blood vessel to collect the sample. You will feel a tiny pinprick during the procedure. Blood sample once collected will then be sent to the laboratory.
- Is there any risk associated with this test?
There is no risk associated with the test. However, since this test involves a needle prick to withdraw the blood sample, in very rare cases, a patient may experience increased bleeding, hematoma formation (blood collection under the skin), bruising or infection at the site of needle prick.
- Is there any preparation required before the test?
Inform the doctor about the medications you may be taking. No other specific preparations are usually required before this test.
- Are there other blood types apart from the ABO and Rh blood types?
Apart from the ABO and Rh blood groups, human blood has been classified into more than 200 blood types under different grouping systems. These are less commonly used and are called minor or rare blood groups. These are not detected by the blood grouping test but are detected only by an RBC screening test for different antigens.
- Which blood groups are known as universal donors and recipients?
Individuals of blood type O Rh- are known as universal donors since they do not have antigens A, B, or Rh on their RBCs, which allows their blood to be transfused safely without any reaction from the recipient. Individuals with blood type AB Rh+ are called universal recipients since they recognize all A, B, and Rh antigens as self and do not produce antibodies against any of these, allowing them to safely receive all blood types without a harmful reaction
Hemolytic Disease of Fetus and Newborn or HDFN is a condition where the blood type of the fetus is incompatible with the blood type of the mother. The most severe reactions typically occur due to Rh incompatibility, where antibodies are produced in the Rh negative mother against Rh positive fetus. These antibodies cross the placenta and react with the RBC of the fetus, causing HDFN.
INTERPRETATION OF THE RESULTS:
Normal reference ranges of Factor VIII activity according to age group is:
- 0 – 1 day: 61 – 139%
- 2 – 5 days: 55 – 121%
- 6 – 30 days: 58 – 124%
- 31 – 90 days: 56 – 102%
- 91 – 180 days: 55 – 91%
- 6 months – 5 years: 59 – 142%
- 6 – 10 years and for all adults: 55 – 120%
Incase of factor VIII abnormal results:
- Mild hemophilia A: 5% to 50% activity
- Moderate hemophilia A: 1% to 5% activity
- Severe hemophilia A: <1% activity
Increased factor VIII activity can be due to liver disease.
You get tested for diagnosing hemophilia A, von Willebrand (vWF) disease, acquired deficiency states; investigating prolonged activated PTT, & for monitoring treatment for hemophilia A.