If the rheumatoid factor is very high in a person diagnosed with rheumatoid arthritis, does this determine the severity of the disease?

Answer: 

Rheumatoid factor is an antibody protein that can be detected in the blood of some people with RA. Another type of antibody is directed against cyclic citrullinated peptide, also called CCP. The presence of both of these in the blood of a person with RA is associated with more severe RA, but not invariably so. It is a biomarker and, as such, may guide treatment choices and predict outcome. However, each person with RA differs from every other one and decisions are made in partnership between the doctor and the patient, employing facts specific to that person. With our amazing new medications, the predictability of such biomarkers will likely mean less.