Rheumatoid factor (RF) is a protein (antibody) made by the immune
system that can attack the body's own tissues. An elevated rheumatoid factor
may mean the presence of an inflammatory disease.
Rheumatoid factor can be measured with a blood test. This is most
helpful for diagnosing rheumatoid arthritis, lupus, and Sjögren's syndrome.
Certain heart and liver diseases, infectious diseases (such as tuberculosis),
and normal aging may also increase RF levels.
How this information was developed to help you make better health decisions.