What is the rheumatoid factor test?

This test checks for an antibody called rheumatoid factor in your blood. Antibodies are the proteins your immune system makes to fight infections. If you have an autoimmune disease, like rheumatoid arthritis, your body also makes antibodies that attack your normal, healthy tissues–for example, skin, blood vessels, or joints.

Why is this test done?

The test is done to help diagnose rheumatoid arthritis. Rheumatoid arthritis is an autoimmune disease that causes pain, stiffness, swelling, and loss of movement in your joints. It can also affect other parts of the body.

How do I prepare for this test?

Usually no preparation is needed for this test.

Talk to your healthcare provider if you have any questions about the test.

How is the test done?

Having this test will take just a few minutes. A small amount of blood is taken from a vein in your arm with a needle. The blood is collected in tubes and sent to a lab.

Ask your healthcare provider when and how you will get the result of your test.

What does the test result mean?

A positive test result means that you have rheumatoid factor in your blood. If you have painful joint swelling and other symptoms along with other abnormal blood test results, you may have rheumatoid arthritis. If you have no symptoms, the test is not very helpful. Many healthy people test positive for small amounts of rheumatoid factor, but they never develop rheumatoid arthritis.

If you have a negative rheumatoid factor test result and no symptoms of arthritis, you probably do not have rheumatoid arthritis. However, some people with rheumatoid arthritis never test positive for rheumatoid factor. Or they may start having a positive test after they have had arthritis for awhile. Other tests can help see if the problem really is rheumatoid arthritis.

What if my test result is not normal?

Test results are only one part of a larger picture that takes into account your medical history, physical exam, and current health. Sometimes a test needs to be repeated to check the first result. Talk to your healthcare provider about your result and ask questions, such as:

• If you need more tests
• What kind of treatment you might need
• What lifestyle, diet, or other changes you might need to make