what is rheumatoid factor
Rheumatoid factor (RF) facts. 1  Rheumatoid factor is an antibody that is detectable in the blood of approximately 80% of adults with rheumatoid arthritis.2  Sometimes rheumatoid factor can be detected in the blood of normal individuals and of those with other autoimmune diseases that are not rheumatoid arthritis.heumatoid factor (RF) facts. 1  Rheumatoid factor is an antibody that is detectable in the blood of approximately 80% of adults with rheumatoid arthritis.