Well...all I could say is that one of my sons was project manager for one of the newer injectable RA drugs and in trials, many many people who had positive RA factor readings did not have the disease...others did NOT test positve and it was concluded they did have it. I have a friend who has been treated for RA since she was 11 years old and never had a positive RA factor and the doctors have just been treating her for the obvious symptoms. I guess the blood testing is just not an exact science. I know that ANA's can change from day to day and many doctors do not use this as a guideline for autoimmune disease anymore. Hopefully someone else with more knowledge will come along.
Donna