You need an MRI of joints to see erosions......xrays do not always work......really high percentage of patients are serum neg......I was for the most part serum neg....but clinically I had RA.......It really makes a difference what Dr. you have and if he is agressive in treating.....you can never get back what you lose from joint errosion. So don't mess around if you do not like what your doctor tells you find another if you can.