Is Rheumatoid Arthritis Diagnosed Purely Based On Blood Tests?

"I am a 33 year old female that had joint pain/swelling for about a period of one week. In the middle of that week I went to the doctor for my symptoms and the doctor took blood to test for many things but said my problem seemed to point to a virus: parvo virus. After researching, it all made sense since I am a 4th grade teacher and fifth disease was in our school at that time. Based on the research I did, parvo virus is the same virus as fifth disease in children. Anyway, the symptoms disappeared in about a week and everything was all better. When the doctor called with my blood work they said I tested positive for the rheumatoid factor (107) and referred me to a rheumatologist. I have an appt. with the rheumatologist in 3 weeks - that was the soonest they could get me in. In the meantime I was sent my blood work results and am concerned about some of the numbers and no one from my regular doctor has called me back. Like I said, my rheumatoid factor was 107 and my ana titer was 1:160 with a homogeneous & nucleolar pattern. Also, I am positive for the parvo virus according to the blood work. I am so confused by what this means and would like some clarification if possible since I do not see the doctor for three weeks. My symptoms have disappeared and I feel fine. Today, however, I feel like my muscles in my upper arms are sore and I haven't done anything that would have made them sore - not sure if this is coincidence or something else to be concerned about. My grandma also had rheumatoid arthritis so it does run in my family. If I had parvo virus could that have affected my blood work and made my rheumatoid factor and ana titer positive? How do doctors diagnose rheumatoid arthritis - is it purely based on the blood test or other things as well? Thank you so much for your help,Jennifer