Rheumatoid Factor

This is a test used to help diagnose rheumatoid arthritis (RA), Sjögren's syndrome, or other autoimmune diseases. This test detects evidence of rheumatoid factor (RF), which is a type of autoantibody. An antibody is a protective protein that forms in the blood, typically in response to a foreign material, usually another protein known as an antigen. Autoantibodies, however, are antibodies that are capable of targeting one's own proteins rather than those of an outside agent, such as bacterial protein. Rheumatoid factors are autoantibodies directed against a fragment of the class of immunoglobulins known as IgG and are members of a class of proteins that become elevated in states of inflammation. Rheumatoid factor is elevated in almost all patients with inflammation and is, therefore, a sensitive test for monitoring the level of inflammation associated with rheumatoid arthritis. It is not a diagnostic test, however, due to its low specificity. Experts still do not understand exactly how RF is formed or why, but it is believed that RF probably does not directly cause joint damage but that it helps to promote the body's inflammation reaction, which contributes to the tissue destruction seen in rheumatoid arthritis.

PREPARATION FOR TEST

A blood sample is obtained by inserting a needle into a vein in the arm.

NORMAL FINDINGS

Negative (Less than 60 units/mL by nephelometric testing); elderly patients may have slightly increased values.

Ranges for normal findings may vary among different laboratories and hospitals. You should always check with your doctor after having lab work or other tests done to discuss the meaning of your test results and whether your values are considered within normal limits.

MEANING OF TEST

Your caregiver will go over the test results with you and discuss the importance and meaning of your results, as well as treatment options and the need for additional tests if necessary.

OBTAINING THE TEST RESULTS

It is your responsibility to obtain your test results. Ask the lab or department performing the test when and how you will get your results.