Use

Rheumatoid Factor (RF), particularly the IgM isotype, is an autoantibody commonly found in the blood of patients with rheumatoid arthritis (RA) and can also be elevated in other autoimmune diseases or chronic infections, as well as in elderly individuals without disease ([jdos.nicholsinstitute.com](https://jdos.nicholsinstitute.com/dos/yorkhospital/test/590568?utm_source=openai)).