Factor VIII Test: Procedure, Purpose, Results, Normal range, Cost, Price, Online testing

What is Factor VIII test?

Factor VIII, or clotting factor VIII is a type of blood clotting protein produced by the body. It works with a cascade of other clotting factors to form a mesh at the injury site that stops bleeding. If the level of any of these factors is low, the whole process gets disrupted and the person gets prone to uncontrolled bleeding. There are different tests to evaluate each clotting factor. The factor VIII test measures the activity of clotting protein VIII.

It is mainly done to diagnose a hereditary disorder called haemophilia A. People who have this disorder have dysfunction or a deficiency of factor VIII. They tend to get unexplained bruises, nosebleeds and excessive bleeding from cuts and wounds.

Haemophilia A is linked to a faulty gene on the X chromosome. It usually affects males because they only have one X chromosome. Females have two X chromosomes, so a faulty gene on one X chromosome can be masked by a normal gene on the other. Females get haemophilia A only when they inherit faulty genes from both parents.

The severity of haemophilia A can also be determined by the activity levels of factor VIII. However, since different clotting factors are involved in the formation of a blood clot, this test may be ordered as part of an overall screening for these factors.

Why is a Factor VIII test performed?
How do you prepare for a Factor VIII test?
How is a Factor VIII test performed?
Factor VIII test results and normal range

Why is a Factor VIII test performed?

Your doctor may order this test if you have a history of unexplained bleeding episodes or if any of your family members have an inherited bleeding disorder.

Symptoms of a bleeding disorder include:

Prolonged, unexplained bleeding after minor cuts, surgeries and dental procedures
Frequent gum bleeding and nose bleeds
Severe low back pain, usually on one side
The need for blood transfusion after a minor injury
Joint pain and stiffness
Heavy menstrual flow
Slow wound healing due to recurrent bleeding and infections
Swollen and hot joints or deformities
Easy bruising

This test may also be ordered to check the effectiveness of the ongoing treatment for haemophilia A.

How do you prepare for a Factor VIII test?

You do not need any special preparation before this test. Inform your doctor if you are taking any prescription and non-prescription medicines and supplements. He/she may ask you to discontinue certain painkillers and blood thinners before the test. Please do not stop taking any medicines without consulting your doctor.

How is a Factor VIII test performed?

Factor VIII test is a simple test performed on a blood sample. A laboratory technician or nurse will withdraw the required amount of blood from a vein in your arm using a sterilised needle. The blood sample will then be transferred to a specialised container and sent to the laboratory for testing.

After the test, you may experience some pain and bruising at the site of needle insertion; however, these symptoms will subside soon. People with bleeding disorders are at a slightly greater risk of bleeding after a blood sample is taken. If you notice persistent blood flow from the needle insertion site, please inform your doctor.

Factor VIII test results and normal range

Normal results:

The factor VIII test results are typically reported as a percentage - it denotes the activity level of factor VIII observed in your blood sample. The result is considered normal when it is around 100% of the laboratory reference value.

Usually, all laboratories have a normal value range of 50-200% of the reference value. However, this range can vary slightly from one laboratory to another.

Abnormal results:

If the value reported in the results is out of the range of normal values, it is considered abnormal. Lower than normal values may be due to the following reasons:

Haemophilia A (6-50% activity is considered mild; 1-5% activity is moderate; and less than 1% is deemed severe)
Von Willebrand disease (a bleeding disorder)
Presence of an antibody against factor VIII in the blood
Disseminated intravascular coagulation (DIC; a disorder where the proteins that keep a check on the clotting process become overactive)

A higher than normal value may show up in the following cases:

Inflammation
Old age
Diabetes
Liver disease
Obesity
Pregnancy

Your doctor may order several more tests to confirm the diagnosis. He/she may also need to perform some genetic tests to understand if haemophilia A runs in your family.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.

References

UCSF health: University of California [internet]; Factor VIII Assay
American Association for Clinical Chemistry.[internet]. Washington DC (U.S.A). Testing for Factor VIII in Hemophilia Care
University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; Factor VIII (Antihemophilia Factor A)
Carcao M, Moorehead P, Lillicrap D. Hemophilia A and B. In: Hoffman R, Benz EJ, Silberstein LE, et al, eds. Hematology: Basic Principles and Practice. 7th ed. Philadelphia, PA: Elsevier; 2018:chap 135.
Chernecky CC, Berger BJ. Factor VIII (antihemophilia factor, AHF) - blood. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. St Louis, MO: Elsevier Saunders; 2013:504-505.
Napolitano M, Schmaier AH, Kessler CM. Coagulation and fibrinolysis. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. St Louis, MO: Elsevier; 2017:chap 39.
National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Blood Tests