Does this test have other names?
APA, lupus anticoagulant, anticardiolipin antibodies
What is this test?
This blood test checks for antiphospholipid antibodies. These may be found in people
with abnormal blood clots or autoimmune diseases.
Your immune system usually creates antibodies in response to an infection or foreign
invaders like bacteria. Antiphospholipid antibodies are usually made when your immune
system mistakes part of your own body for a harmful substance. In this case, the antibodies
seem to be reacting to phospholipids. Phospholipids are a normal part of your blood
People who have abnormal blood clots, repeated miscarriages, or autoimmune diseases
like lupus and multiple sclerosis often have antiphospholipid antibodies. People with
cancer may also have these antibodies. The antibodies often fade away when the cancer
The two most common types of antiphospholipid antibodies are lupus anticoagulant and
anticardiolipin antibodies. Testing for lupus anticoagulant often uses a test like
the Russell viper venom time (RVVT) or kaolin clotting time. RVVT measures how long
it takes a type of viper venom to trigger a blood clot. Kaolin clotting time is used
to diagnose clotting disorders and find the lupus anticoagulant. Measuring anticardiolipin
antibodies is done by looking for antibodies against the cardiolipin molecule.
Why do I need this test?
You may need this test if you:
Have repeated miscarriages
Get abnormal blood clots that could lead to heart attack or stroke
Have antiphospholipid antibody syndrome. This is a group of symptoms that includes
miscarriages, a platelet deficiency, and abnormal blood clots.
Have lupus or cancer
What other tests might I have along with this test?
Your health care provider may also order a partial thromboplastin time, or PTT. This
may help find out what is causing a blood clot or bleeding disorder. You may also
have a dilute prothrombin test. This helps measure how long it takes a clot to form.
What do my test results mean?
Many things may affect your lab test results. These include the method each lab uses
to do the test. Even 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 health
A negative result means you don’t have these antibodies. Low to moderate results may
mean the antibodies are there because of a recent health problem or a drug you have
taken. High levels of this antibody may mean you have a higher risk for blood clots.
Your health care provider cannot predict when a clot may happen. Your doctor may order
a second test in about 12 weeks to confirm the results.
A positive result does not mean you need treatment. If you have antiphospholipid syndrome,
your provider may suggest treatment that includes warfarin, an anti-clotting medicine.
Your provider will tell you what the results mean in light of your overall health.
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 test done for syphilis can cause a false-positive antiphospholipid antibody test
result if done at the same time. That’s because the substances used to test for syphilis
have phospholipids in them. Your health care provider may order a second test to confirm
Some drugs such as quinidine, procainamide, phenytoin, and penicillin may raise antibody
levels. Recent viral infections such as HIV can also affect the results.
How do I get ready for this test?
You don't need to prepare for this test. But be sure your doctor knows about all
medicines, herbs, vitamins, and supplements you are taking. This includes medicines
that don't need a prescription and any illicit drugs you may use.