Rheumatoid factor (RF) facts
- Rheumatoid factor is an antibody that is detectable in the blood of approximately 80% of adults with rheumatoid arthritis.
- Sometimes rheumatoid factor can be detected in the blood of normal individuals and of those with other autoimmune diseases that are not rheumatoid arthritis.
- In people with rheumatoid arthritis, high levels of rheumatoid factor can indicate a tendency toward more aggressive disease and/or a tendency to develop rheumatoid nodules and/or rheumatoid lung disease.
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?
Most commonly, rheumatoid factor is 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.