Autoantibody tests do but are not necessarily an indication of disease activity which is why most docs don't test after getting a diagnosis. They do go up and down. How you feel is more of an indicator of what's going on.
RNP is tested to see if you have an overlap syndrome, MCTD. Once it is positive it is usually not tested again. No reason. Often other tests are ordered to confirm a diagnosis....like a biopsy or some other diagnostic test.
MCTD (SLE Lupus, polymyositis, scleroderma). Diagnosed 2005. Kidney, liver, GI tract, dysphagia, raynauds, barretts esophagus, quadriplegic in 2005. Recovered and now active in downhill skiing, golf, hiking. Meds: amlodipine, benezapril, omeprazole, potassium, folic acid, vitamins, maxide.
Remain Optimistic and you can overcome.