How is it possible for someone to have rheumatoid arthritis with a negative rheumatoid factor?

Negative RA test: Yes. About 10% of cases have a negative RA test though sometimes newer tests can still be positive.

Great question!: Rheumatoid arthritis (RA) is a disease that generally causes stiffness, swelling, and pain of the small joints of the body (wrists, fingers) in a symmetric manner. For the majority of patients with RA, rheumatoid factor and anti-CCP antibodies are found in the blood. However, these tests are not required to make the diagnosis if there are other findings on exam that are consistent with RA.