Hi S,
I'm sorry I did not see this until this morning. The fact that ANA is negative is a very good thing. That may rule out AI diseases like Lupus, Sjogren's others associated with ANA. If you show a positive lab to Rf, then there is a higher probability of RA. According to a book I have on the Rf lab test, the odds are 75% that it's RA but that leaves a 25% chance that it could be something else. That's why it's important that your Rheumatologist continues to examine your signs and symptoms. There are other criteria for a diagnosis. And remember catching any disease development in it's early stage is a very good thing. With a little work and medication it's possible to keep it at bay for years or forever.
I found a support board sponsored by the Arthritis foundation where you might find a few more answers and questions to ask your new Rheumatologist on your first appointment. Let me know if this is helpful and I'll make another post for this support community. I do seem to get a few clients with RA or at least the beginning stages of it.
http://community.arthritis.org/forums/Topic4284586-1831-1.aspx
One last thing....gluten sensitivity and Celiac disease are highly associated with RA. A gluten-free diet has been shown to reduce inflammation in the body...also reducing RA symptoms.