Classifi cation of RA
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The American College of Rheumatology originally classifi ed RA in the 1980s (Arnett 1988). However these criteria are no longer as relevant mainly due to the success of current treatments (two of the seven criteria, nodules and erosions are generally not present at early diagnosis). The EUropean League Against aRthritis (EULAR) developed classifi cation criteria which devised a score based on 28 joints, an infl ammatory marker and a global health assessment score (Van Gestel 1999). This classifi cation system has been used both to select patients for clinical trials and to monitor a patient’s response to treatment. A joint initiative between ACR and EULAR re-examined the classifi cation criteria for RA with a focus on early disease and these new classifi cation criteria have been published (Aletaha et al. 2010). The classifi cation described, establishes a diagnosis of RA. The next step required for outcome measurement is to defi ne a health state which may be mild, moderate or severe RA. Improved classifi cation systems for RA have strengthened the studies on epidemiological evidence which were diffi cult to compare prior to this robust classifi cation criteria.