Rheumatoid Arthritis Support Group
Rheumatoid arthritis is a chronic, inflammatory, multisystem, autoimmune disorder. It is a disabling and painful condition which can lead to substantial loss of mobility due to pain and joint destruction. The disease is also systemic in that it often also affects many extra-articular tissues throughout the body including the skin, blood vessels, heart, lungs, and...

Any rheumatologist who has been in practice for a few decades will tell you that we live in a whole new world. There are several types of therapies available, and the biologic drugs in particular (Humira, Enbrel, etc.) have made for far better outcomes than your grandmother's generation could hope for. Don't assume you will end up like she did.
With any medical test the two things that will bite you are false negatives, a test that says you're fine when you are not, and false positives, where the test says you are sick when you are actually as healthy as the proverbial horse. My uneducated guess is that the 87% figure is how likely it is that you do indeed have RA. It could also refer to the chance of showers that day, or the percentage of people at the lab who skipped breakfast!
Have you seen a rheumatologist? If not, do you have an appointment pending?
I have Osteo arthritis, bursitis, tendonitis, and Osteopenia, in addition to the RA.
My Rheum treated me aggressively.I am on methotrexate, and a biologic. Because of this, the majority of the time, I feel pretty good. Most of the time, I do not take anything for pain. I do, occasionally, take a Celebrex, but not often. I am having problems with my grip, I make adjustments for that.
Hopefully, your Rheum will be aggressive in his treatment, and not do a 'wait & see'. You probably won't find the drug combination that works right away - I know mine took a while to get the right drug. Good luck.