Factor II Assay

Written by Corinna Underwood | Published on August 7, 2012
Medically Reviewed by Brenda B. Spriggs, MD, MPH, FACP

What is a Factor II Assay?

Your doctor may recommend a factor II assay (test) to determine if your blood clots correctly.

Factor ll is known as prothrombin and it is one of the substances in blood responsible for blood clot formation. If your blood has trouble clotting, you may be at risk for episodes of prolonged or excessive bleeding. This factor assay is used to measure whether the level of factor II in your blood is too low.

Each time you bleed, it triggers a series of reactions known as the “coagulation cascade.” Coagulation is the process your body uses to stop blood loss. Cells, called platelets, create a plug to cover the damaged tissue. Then, your body’s clotting factors interact to produce a blood clot. Low levels of clotting factors can prevent a clot from forming.

Seek immediate medical help if you experience a sudden or prolonged loss of blood.

What the Test Addresses

This test is used to determine the cause of excessive bleeding. Your doctor may recommend the test if you have a family history of bleeding disorders or if you have experienced any of the following symptoms:

  • bleeding of the umbilical cord stump at birth
  • excessive bleeding after circumcision
  • bleeding after childbirth
  • frequently bleeding gums
  • easy bruising
  • frequent nose bleeds
  • prolonged bleeding after surgery
  • abnormally heavy or prolonged menstrual periods
  • black, tarry stools
  • blood in the urine
  • bleeding in the joint spaces
  • soft-tissue hemorrhages
  • intracranial bleeding

Your doctor may also recommend this test if he or she suspects that you have:

  • vitamin K deficiency (Vitamin K is required for the production of clotting factors in the liver)
  • liver disease
  • an inherited blood factor deficiency

Severity of Symptoms

Your body produces 13 different coagulation factors that must all be present in order for the clotting process to proceed normally. The severity of your symptoms will depend on the type of factor deficiency you have, the way in which the particular factor functions, and the amount of factor your body makes.

Symptoms may also vary from bleeding episode to bleeding episode. For example, on one occasion you may experience excessive gum bleeding after a dental procedure, while during another episode you may have blood in your stool or urine.

If your level of coagulation factor is moderately low, you may experience few symptoms and may not become aware of the deficiency until after a surgical procedure. However, if you have a severe factor deficiency, you will have experienced excessive bleeding at an early age, perhaps even in infancy.

Preparation for the Test

No special preparation is necessary for this test. You should tell your doctor if you are taking any blood-thinning medications such as warfarin (Coumadin). Your doctor may advise you to stop taking blood thinners before the test.

Where and How is the Test Administered

Your doctor will usually order the test during a period of excessive bleeding or bruising.

To perform the test, your doctor will need to take a sample of blood from your arm. First the site will be cleaned with an alcohol swab. Then, the doctor will insert a needle into your vein and attach a tube to the needle to collect blood. When enough blood has been collected, the needle will be removed and the site, and mild pressure is applied with a gauze pad. The blood sample will be sent to a laboratory for analysis.

Understanding the Results

Normal Results

A normal result for a factor II assay should be between 50 and 200 percent of the laboratory control value. Your doctor will explain the specifics of your results.

Abnormal Results

If your results are abnormal, it means that you have a low level of factor II. This could be caused by:

  • congenital factor II deficiency (present at birth)
  • fat malabsorption
  • liver disease (cirrhosis)
  • vitamin K deficiency
  • disseminated intravascular coagulation or DIC (a disease in which the proteins responsible for blood clotting are abnormally active)
  • use of warfarin (Coumadin)

What are the Risks of the Test?

As with any blood test, there is a slight risk of bruising or bleeding at the puncture site. In rare cases, the vein may become swollen after blood is drawn. This condition, known as phlebitis, can be treated by applying a warm compress several times a day.

Ongoing bleeding could be a problem if you suffer from a bleeding disorder or are taking blood-thinning medication, such as warfarin or aspirin.

Following Up After the Test

Your doctor may order further factor assays to ensure that the levels of your other coagulation factors are normal. He or she may also order other blood analyses to determine the cause of your low level of factor II.

If you need supplemental factor II, you may receive a transfusion of fresh frozen blood plasma that contains your missing factor or factors. You may receive this treatment during an episode of bleeding, or prior to surgery or a dental procedure.

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