I will tell you my own story which is similar to yours. I was in the exact same position as you in 2013. Same symptoms and same bloodwork and I suspected RA on top of my UC. However, and this is important, my UC was flaring back then as well and that ultimately was what was causing my joint issues. I started Imuran and it put both my bowel and joint issues into remission and they have been since 2013.
I still have high ANA and RF and always will. However, neither my GI nor my Rheumy believe this was RA. It could be that I develop RA at some future time-point however as of now I do not have this. Both say the joint issues were a form of reactive or enteropathic arthralgia that was induced by inflammation or immune activity in the bowel. In particular my joint symptoms were flitting, non-swelling and actually presented more in the tendons than the joint themselves. I'm sure some of what I had was enthesitis and dactylitis neither of which are consistent with RA (but are consistent with the Spondyloarthropathies of which IBD arthralgia is one of them).
The important point is that blood markers are not on their own an indication of a certain disease or condition. RA cannot be diagnosed based on positive ANA and RF alone. It needs to be diagnosed by a Rhumey in relation to your whole body and symptom presentation. Too many of us are reading incorrect web literature and immediately associating certain disease and conditions with certain positive blood markers. This is absolutely incorrect and as any good doctor will tell you more especially for the vagueness that surrounds autoimmune conditions.
Now it actually turns out that I am currently having some joint issues and unusual bodily symptoms and I have again questioned the RA diagnosis with my GI and Rheumy and again, on physical examination and X rays and MRIs, I fail the RA criteria and they put my symptoms down to mild bowel activity which is inducing reactive effects.
For you good to have further RA testing done by your Rheumy but the fact that your UC is active here is highly suspicious of another explanation. Try a topical steroid such as Entocort which is specific to inflammation in the bowel and if this also provides significant improvement for your joint issues then that would point away from true independent rheumatic conditions being present.
Finally you mention that you read that 30% of UCers experience RA. That is not correct. What you likely read is that 30% of UCers experience joint issues of which the vast vast majority are forms of IBD arthalgia, AS or other forms of SpA. RA is just one of the many forms of joint conditions which run into the hundreds. To have PsA or RA would imply an independent and separate autoimmune condition and memory serves that that % is under 2 or 3.
Post Edited (damo123) : 8/1/2021 4:20:15 AM (GMT-6)