Factor IX assay
Christmas factor assay; Serum factor IX; Hemophilic factor B; Plasma thromboplastin component; PTCThe factor IX assay is a blood test that measures the activity of factor IX. This is one of the proteins in the body that helps the blood clot.
How the Test is Performed
A blood sample is needed.
Blood sample
Venipuncture is the collection of blood from a vein. It is most often done for laboratory testing.
Read Article Now Book Mark ArticleHow to Prepare for the Test
You may need to stop taking some medicines before this test. Your health care provider will tell you which ones.
How the Test will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or slight bruising. This soon goes away.
Why the Test is Performed
This test is used to find the cause of too much bleeding (decreased blood clotting). Or, it may be ordered if a family member is known to have hemophilia B. The test may also be done to see how well treatment for hemophilia B is working.
Hemophilia B
Hemophilia B is a hereditary bleeding disorder caused by a lack of blood clotting factor IX. Without enough factor IX, the blood cannot clot properl...
Read Article Now Book Mark ArticleNormal Results
A normal value is 50% to 200% of the laboratory control or reference value.
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or may test different samples. Talk to your provider about the meaning of your specific test results.
The examples above show the common measurements for results for these tests.
What Abnormal Results Mean
Decreased factor IX activity may be related to:
-
Hemophilia B (a bleeding disorder caused by a lack of blood clotting factor IX)
Hemophilia B
Hemophilia B is a hereditary bleeding disorder caused by a lack of blood clotting factor IX. Without enough factor IX, the blood cannot clot properl...
Read Article Now Book Mark Article - Disorder in which the proteins that control blood clotting become overactive (disseminated intravascular coagulation)
Disseminated intravascular coagulation
Disseminated intravascular coagulation (DIC) is a serious disorder in which the proteins that control blood clotting become overactive.
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Malabsorption
Malabsorption involves problems with the body's ability to take in (absorb) nutrients from food.
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Liver disease (such as cirrhosis)
Liver disease
The term "liver disease" applies to many conditions that stop the liver from working or prevent it from functioning well. Abdominal pain or swelling...
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Cirrhosis is scarring of the liver and poor liver function. It is the last stage of chronic liver disease.
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Vitamin K deficiency
Vitamin K
Vitamin K is a fat-soluble vitamin. Your body stores vitamin K in the liver and other body tissues, including the brain, heart, pancreas, and bone....
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Risks
There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another, and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight, but may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Multiple punctures to locate veins
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
This test is most often done on people who have bleeding problems. The risk of excessive bleeding is slightly more than for people without bleeding problems.
Bleeding problems
Bleeding disorders are a group of conditions in which there is a problem with the body's blood clotting process. These disorders can lead to heavy a...
Read Article Now Book Mark ArticleReferences
Carcao M, Gomez K, Davide M, Pierce GF. Hemophilia A and B. In: Hoffman R, Benz EJ, Silberstein LE, et al, eds. Hematology: Basic Principles and Practice. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 134.
Pai M, Moffat KA. Laboratory evaluation of hemostatic and thrombotic disorders. In: Hoffman R, Benz EJ, Silberstein LE, et al, eds. Hematology: Basic Principles and Practice. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 127.
Ragni MV. Hemorrhagic disorders: coagulation factor deficiencies. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 165.
Review Date: 2/2/2023
Reviewed By: Mark Levin, MD, Hematologist and Oncologist, Monsey, NY. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.