Antiphospholipid Antibody

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 vessels.

People who have abnormal blood clots, repeated miscarriages, or autoimmune diseases, such as systemic lupus erythematosus (SLE) and multiple sclerosis often have antiphospholipid antibodies. People with cancer may also have these antibodies. The antibodies often fade away when the cancer is treated.

The 2 most common types of antiphospholipid antibodies are lupus anticoagulant and anticardiolipin antibodies. Testing for lupus anticoagulant often uses a test, such as 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 SLE or cancer

• Have an unexpectedly prolonged and activated partial thromboplastin time (aPTT) 

What other tests might I have along with this test?

You may also need an aPTT. 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?

Test results may vary depending on your age, gender, health history, and other things. Your test results may be different depending on the lab used. They may not mean you have a problem. Ask your healthcare provider what your test results mean for you.

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 medicine you have taken. High levels of this antibody may mean you have a higher risk for blood clots. Your healthcare provider can't predict when a clot may happen. You may need a second test in about 12 weeks to confirm the results.

A positive result doesn't mean you need treatment. If you have antiphospholipid syndrome, your provider may suggest treatment that includes warfarin, an anticlotting medicine. Your provider will tell you what the results mean in light of your overall health. 

How is this test done?

The test is done with a blood sample. A needle is used to draw blood from a vein in your arm or hand. 

Does this test pose any risks?

Having a blood test with a needle carries some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be 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. You may need a second test to confirm the results.

Some medicines may raise antibody levels. These include quinidine, procainamide, phenytoin, and penicillin. 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. Tell your healthcare provider about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illegal drugs you may use.