Does this test have other names?
Factor V assay, clotting factor tests
What is this test?
A factor V test is a blood test that checks for a deficiency in a protein known as
factor V. Factor V is a protein that helps your blood to clot. Having too little factor
V causes a rare bleeding disorder. Your body has a number of protein "clotting factors."
They are identified by Roman numerals.
Factor V deficiency is an inherited disorder. It is called an autosomal recessive
gene disorder. This means both parents must have the defective gene and pass it on
to their children for this to occur.
Why do I need this test?
If you have certain symptoms, such as unexplained or extra bleeding or bruising, it
may mean that your blood is not clotting the way it should. You might have a deficiency
in one of the clotting factors. Your healthcare provider may do a blood test to check
for the presence and function of the individual clotting factors to see if you have
a deficiency in any of them.
What other tests might I have along with this test?
Along with tests to check for factor V deficiency, your healthcare provider might
check your blood for deficiencies in other clotting factors.
What do my test results mean?
A result for a lab test may be affected by many things, including the method the laboratory
uses to do the test. If your test results are different from the normal value, you
may not have a problem. To learn what the results mean for you, talk with your healthcare
In a test of your clotting factors, the results are usually given as a percentage.
So if you get a result of 100%, it means your factor V is at 100% of its normal value.
Levels between 25% and 60%mean a mild factor V deficiency. This usually causes no
symptoms. Levels of 1% to 10% are severely low and can lead to major bleeding issues.
How is this test done?
The test requires a blood sample, which is drawn through a needle from a vein in your
Does this test pose any risks?
Taking a blood sample with a needle carries risks that include bleeding, infection,
bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight
stinging sensation or pain. Afterward, the site may be slightly sore.
What might affect my test results?
A deficiency of factor V is quite rare (about 1 in 1 million) and can be a genetic
disorder passed on from parents to their children. But some clotting factors, including
factor V, can decrease because of certain illnesses, such as liver disease, cancers,
autoimmune diseases, and a disease called disseminated intravascular coagulation.
It can also occur after exposure to some toxins.
How do I get ready for this test?
You don't need to prepare for this test.