Rheumatoid Factor (RF) Test Test
A rheumatoid factor (RF) test measures the level of rheumatoid factor in your blood. High levels may be a sign of autoimmune disorders like rheumatoid arthritis, but the test alone cannot diagnose a condition.
What this test measures
The RF test checks your blood for rheumatoid factor, a protein made by the immune system that attacks healthy cells instead of germs.
What your results mean
Reference ranges vary by laboratory and by your age and sex. MedlinePlus does not publish a single normal range for this test — always read your result against the range printed on your own lab report and discuss it with your provider.
Higher-than-normal results
A positive (abnormal) result means a higher level of rheumatoid factor was found. It may indicate rheumatoid arthritis, another autoimmune disease, a chronic infection, or certain cancers, but further testing is needed.
Lower-than-normal results
A negative (normal) result means little or no RF in your blood, but it does not rule out rheumatoid arthritis or other health problems.
Frequently asked questions
What is rheumatoid factor?
Rheumatoid factor is a protein made by the immune system that attacks healthy cells, usually immunoglobulin G.
Can I have high RF and still be healthy?
Yes, many people have small amounts of RF and are healthy. Even high amounts aren't always a sign of a health condition.
Does a negative RF test rule out rheumatoid arthritis?
No, a negative result does not rule out rheumatoid arthritis. Your provider may order more tests if you have symptoms.
What does a positive RF test mean?
A positive result means a higher level of RF was found. It may indicate rheumatoid arthritis, another autoimmune disease, chronic infection, or certain cancers.
How is RF testing used?
RF testing is mostly used with other tests to help diagnose rheumatoid arthritis and other conditions.
Related lab tests
Sources
- MedlinePlus: Rheumatoid Factor (RF) Test — NIH MedlinePlus
Last updated . Information is aggregated from official public sources and is not a substitute for professional medical care.