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What is Factor IX Test?

Factor IX or coagulating factor IX is one of the clotting proteins produced in the body. It is responsible for preventing excessive bleeding in case of an injury. Deficiency of this protein is usually an indication of a bleeding disorder called haemophilia B. 

Since they lack this clotting factor, people with factor IX deficiency tend to have uncontrolled bleeding every time they get an injury. This may not be a matter of concern in small cuts, however, haemophilia B may be troublesome in case of a severe injury. It may also cause bleeding inside the muscles, joints or other vital organs such as the brain which could be potentially life-threatening.

A factor IX test is used to determine the amount of factor IX in blood to check if you have haemophilia. This test is also known as haemophilia B test, FIX test, Christmas disease test, factor IX haemophilia test and factor IX deficiency test. 

  1. Why is a Factor IX test performed?
  2. How do you prepare for a Factor IX test?
  3. How is a Factor IX test performed?
  4. What do Factor IX test results mean?

Haemophilia is a genetic condition - it runs in families. Doctors order a factor IX test:

  • To pregnant women who have a family history of bleeding disorders
  • For the newborn of a woman who is suffering from this condition with a retest after six months to confirm the presence of the condition in the infant
  • If multiple unusual bruises are observed in older children
  • To assess the efficacy of the treatment for haemophilia
  • If you tend to bleed a lot after getting vaccinated or get frequent nosebleeds 
  • If you get bleeding in the joints without a known cause 

People who have a milder form of haemophilia may show signs and symptoms once they are older. So, if you have a history of unusual bleeding problems your doctor may ask for this test to rule out haemophilia.

You do not require any special preparation for this test. Inform your healthcare provider if you are consuming any medicines, vitamins and supplements. This information should also include the medications that do not need any prescription or any illicit drugs that you may be consuming. Your doctor may ask you to stop taking certain medicines that may affect the test. For example, blood thinners such as heparin need to be stopped two days before this test to prevent false results. 

For this test, a laboratory technician will draw blood from a vein in your arm by inserting a sterile needle.You may feel a slight pinch as the needle goes into the vein. However, apart from that, the test itself is usually risk-free. 

Factor IX values are generally written as a percentage of the pooled plasma.

Normal results:

The normal results for this test range between 50%-100% of the standard value. It indicates that the required amount of factor IX is present in your body.

Abnormal results:

If the results are below the normal range, it shows the presence of haemophilia. The severity of the disorder may be categorised as follows:

  • Mild haemophilia: 5%-50% of the standard or reference value
  • Moderate haemophilia: 1%-5% of the standard or reference value
  • Severe haemophilia: less than 1% of the standard or reference value

Abnormal factor IX activity may also occur due to liver diseases, fat malabsorption or vitamin K deficiency. Once the disorder is determined, the best treatment can be initiated.

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.

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  1. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; Factor IX (Antihemophilic Factor B)
  2. Genetics Home Reference [internet]. National Institute of Health: US National Library of Medicine. US Department of Health and Human Services; F9 gene: Coagulation factor IX
  3. National Health Portal India. Centre for Health Informatics. National Institute of Health and Family Welfare: Ministry of Health and Family Welfare (MoHFW), Government of India; Haemophilia
  4. UCLA health: University of California [internet]; Factor IX Assay
  5. Center for Disease Control and Prevention [internet], Atlanta (GA): US Department of Health and Human Services; What is Hemophilia?
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