Definition of Rheumatoid factor

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

Rheumatoid factor: An antibody that is measurable in the blood and is used to diagnose rheumatoid arthritis. Rheumatoid factor is present in about 80 percent of adults, and a much lower proportion of children, who have rheumatoid arthritis. It is also present in patients with other connective-tissue diseases, such as systemic lupus erythematosus, and in some patients with infectious diseases, such as infectious hepatitis.