Rheumatoid Factor

1. Rheumatoid Arthritis Slideshow Pictures
2. Take the RA Quiz
3. Rheumatoid Arthritis Exercises Slideshow

Medical Author:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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What is rheumatoid factor?

Rheumatoid factor is an antibody that is measurable in the blood. Rheumatoid factor is actually an antibody that can bind to other antibodies. Antibodies are normal proteins in our blood that are important parts of our immune system. Rheumatoid factor is an antibody that is not usually present in the normal individual.

For what is the rheumatoid factor test used?

Rheumatoid factor is commonly used as a blood test for the diagnosis of rheumatoid arthritis. Rheumatoid factor is present in about 80% of adults (but a much lower proportion of children) with rheumatoid arthritis.

Can rheumatoid factor be present in a patient without rheumatoid arthritis?

Yes. Rheumatoid factor is also present in patients with other conditions, including other connective tissue diseases (such as systemic lupus erythematosus), some infectious diseases (such as infectious hepatitis, syphilis, infectious mononucleosis, parasites, and tuberculosis), liver disease, and sarcoidosis. Rheumatoid factor can also sometimes be present in normal individuals without diseases. This occurs more frequently in people with family members who have rheumatoid arthritis.

What significance does the rheumatoid factor hold for patients with rheumatoid arthritis?

High levels of rheumatoid factor are associated with more severe rheumatoid disease. This factor is also associated with a higher tendency to develop non-joint manifestations of rheumatoid disease, such as rheumatoid nodules and rheumatoid lung disease.