I have a negetive blood test for rheumatiod factor but my sed rate was high and I was anemic. I got diagnosed partly because of the morning stiffness lasting 3-4 hour, high sed rate, both sides of my body were affected and that I reacted so well to Prednisone. My first appointment with my rheumatologist he put me on Enbrel right away. He treated me very aggresive. My RA is sevre and none of the other treatments worked very well. It will eventualy come clear what kind of arthritis you have.