Patient education: Rheumatoid factor test (The Basics)

What is a rheumatoid factor test? — 

This is a test to check the blood for "rheumatoid factor." This is a protein, or antibody, made by the body's infection-fighting system (the "immune system").

Normally, a person's immune system makes antibodies when they get an infection. The antibodies attack the germs causing the infection. If a person's immune system isn't working normally, it sometimes makes antibodies that attack their own body. This is called an "autoimmune disease."

An autoimmune disease called rheumatoid arthritis ("RA") causes the body to make rheumatoid factor. Not everyone with RA has rheumatoid factor in their blood. But the test, along with other tests, can give your doctor information about your health.

Other autoimmune diseases, as well as some types of infection or cancer, can also cause the body to make rheumatoid factor. In some cases, a person can have rheumatoid factor in their blood even though they are healthy.

Why might I get a rheumatoid factor test? — 

Doctors usually order this test in people who have symptoms that could be caused by RA. These include pain and swelling in multiple joints.

Often, doctors order a rheumatoid factor test along with other related tests. One is called an "anti-CCP" test. It looks for a different antibody that is often found in people with RA.

How do I prepare for a rheumatoid factor test? — 

You need to get a "blood draw." Your doctor or nurse will tell you where to go for this.

It might help to wear a short-sleeve shirt to your blood draw appointment. This makes it easier for the person drawing your blood to get to your arm.

What happens during a blood draw? — 

A needle is used to take a small amount of blood from your arm (figure 1). Collecting the blood only takes a few minutes. The blood is then tested in a lab.

Tell the person who takes your blood:

●If you take "blood thinner" medicines or have a bleeding problem – They will make sure your bleeding is under control before you leave.

●If you have a latex allergy – Some of the supplies used for blood draws might contain latex.

●If you have a preferred arm to use

Most of the time, getting blood taken does not cause problems. You might have a little soreness or bruising where the needle went in.

What do my results mean? — 

Your doctor or nurse will tell you when to expect your results, and will contact you with the results. Or if you use an online "patient portal," you might get an alert there when your results are ready.

The test results can be:

●Negative – This means the test found no (or very little) rheumatoid factor in your blood.

●Positive – This means the test found higher-than-normal levels of rheumatoid factor in your blood. The results also show the level of rheumatoid factor.

If your rheumatoid factor test is negative, but you have symptoms like joint pain and swelling, your doctor can do other tests. This can help them figure out if your symptoms are caused by RA or something else.

If your rheumatoid factor test is positive, your doctor or nurse will talk to you about what to do next. A positive test result does not always mean you have RA.

If you do have a health problem, your doctor will work with you to come up with a treatment plan.

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