Rheumatoid Factor Test – Why am I having this test?

The rheumatoid factor test is used to help diagnose certain autoimmune diseases. Normally, your body makes protective proteins called antibodies (IgM, IgG, and IgA) to help fight off infections.

If you have an autoimmune disease, your body may make a collection of antibodies that do not function correctly (autoantibodies). They attack tissues that are wrongly identified as foreign. In some autoimmune diseases, these autoantibodies are known as the rheumatoid factor (RF).

You may have this test if your health care provider suspects that you have an autoimmune disease, such as:

• Rheumatoid arthritis (RA).
• Systemic lupus erythematosus (SLE).
• Sjögren’s syndrome.
• Mixed connective tissue disease.

A majority of people who have rheumatoid arthritis have a positive rheumatoid factor. Raised levels of these autoantibodies can also sometimes be a sign of other autoimmune diseases. However, it is also possible for the RF test to be negative even when a disease is present. Likewise, a small number of people may have a positive RF test when an autoimmune disease is not actually present. Other tests may be needed to help make a diagnosis.

What is being tested?

This test checks your blood for the RF autoantibodies.

What kind of sample is taken?

A blood sample is required for this test. It is usually collected by inserting a needle into a blood vessel or by sticking a finger with a small needle.

How are the results reported?

Your test result will be reported as either positive or negative for RF autoantibodies.

What do the results mean?

A negative result means that no RF or only a small amount was found in your blood. This means that it is unlikely that you have an autoimmune disease.

A positive result means that a larger amount of RF autoantibodies was found in your blood. This may indicate that you have RA or another autoimmune disease. Your health care provider will talk to you about doing more tests to confirm your results.

Talk with your health care provider about what your results mean.

Questions to ask your health care provider

Ask your health care provider, or the department that is doing the test:

• When will my results be ready?
• How will I get my results?
• What are my treatment options?
• What other tests do I need?
• What are my next steps?

Summary

• The rheumatoid factor test is used to help diagnose certain autoimmune diseases.
• In some autoimmune diseases, the body makes autoantibodies known as the rheumatoid factor (RF), which attack tissues that are wrongly identified as foreign.
• A negative result means that no RF or only a small amount was found in your blood.
• A positive result means that a larger amount of RF autoantibodies was found in your blood.
• Talk with your health care provider about what your results mean.