Factor IX assay
Key points
- This is a blood test that measures the activity of factor IX - one of the substances involved in coagulation (blood clotting).
- Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand.
- The health care provider may advise you to stop taking drugs that may affect the test.
- This test is used to detect the specific cause of excessive bleeding (decreased blood clotting).
Alternative names
Christmas factor assay; Serum factor IX
Definition
This is a blood test that measures the activity of factor IX - one of the substances involved in coagulation (blood clotting).
How the test is performed
Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to swell with blood.
A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
For infants or young children, the area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.
How to prepare for the test
The health care provider may advise you to stop taking drugs that may affect the test. (See Special Considerations.)
For infants and children, the preparation you can provide for this test depends on your child's age, previous experiences, and level of trust. For general information regarding how you can prepare your child, see the following:
- infant test or procedure preparation (birth to 1 year)
- toddler test or procedure preparation (1 to 3 years)
- preschooler test or procedure preparation (3 to 6 years)
- schoolage test or procedure preparation (6 to 12 years)
- adolescent test or procedure preparation (12 to 18 years)
How the test will feel
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the test is performed
This test is used to detect the specific cause of excessive bleeding (decreased blood clotting).
Normal Values
A normal value is 50-200% of the laboratory "control" or reference value.
What abnormal results mean
Written and revised by
Andrey Nailor, M.D.
Our doctors write and review articles for accuracy and keep them up to date.
health.am provides general information, not medical advice. Always consult a qualified health professional about your own health.