Hi there and welcome to KA.
Here's the thing, AS is a seronegative arthritis, so testing negative for the rheumatoid factor really only means that you don't have RA. In people with AS, the SED rate (also called ESR) can be quite normal, but inflammation is still present. It is
not an accurate indicator of disease activity in all people with AS. This is prevalent enough among us that it is starting to be recognized by some rheumies. There are certainly enough studies that prove this.
I would suggest you request a nuclear bone scan as soon as you get in with a rheumy, as this will show exactly where in your body the inflammation is. It sure sounds like AS pain, but I'm not a doctor.
Question: is your pain symmetrical (on both sides at once) or asymmetrical (one side only)? For instance, do both heels hurt at the same time, or just one of them? Butt pain on both sides or just one? Thing is, people with RA tend to have pain on both sides at once. People with AS tend to have it on one side only. Maddeningly, in us it tends to switch from day to day, as well. Monday: left neck, right upper back, right lower back, left butt. Tuesday: neck fine, left ribs bad, right lower back, right butt. I call AS the Bits N Bites of the arthritis world - a whole new day, a whole new handful of pain.
The other test I would request is the blood test for HLA-B27. HLA-B27 is a genetic tissue type that only about 10% of the population has, but about 93% of people with AS have.
I hope you don't have AS, but if you do you've found a whole world full of new friends right here.
Hugs,
