This is a great question as it is a very common test that we do in Rheumatology. Rheumatoid factor is a blood test that is done when we are trying to confirm whether a person has Rheumatoid Arthritis.
Rheumatoid Factor is an antibody in the blood that can be present in low levels in some people but is elevated in most people with Rheumatoid Arthritis. However, it also occurs in other conditions such as Lupus and people without joint disease, so its presence doesn’t automatically mean that you have Rheumatoid Arthritis!
RF is an antibody targeting the body’s own immune system. Specifically, its an antibody to an antibody… it is an IgM antibody directed against an IgG antibody.