Established rheumatoid arthritis - Redefining the concept.

During the last few years, there has been a shift of focus in rheumatoid arthritis (RA) research towards earlier disease states. The terms early and established RA are inseparable, and having a clear definition of these two terms is crucial in conducting research and trying to understand the immunopathological mechanisms behind these different disease states. Established RA has been connected to chronic inflammation and a high burden of long-standing disease, with joint damage and comorbidities as a consequence of chronic inflammation. A chronological definition does not ensure us clear differentiation between early and established disease, because diagnosis can be delayed significantly. Similarly, a radiological definition does not ensure a clear differentiation either, as there is significant heterogeneity in the RA patient population, with some patients never developing structural damage, even after many years of disease. As the focus is now more on the early stages of disease, we propose to use the term established RA from the time of a definite clinical diagnosis of RA, irrespective of the symptoms' duration or the presence of irreversible damage, to distinguish established disease to a stage of undifferentiated arthritis (UA) or risk for developing RA, which might never progress to RA.