• rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic systemic inflammatory disease with peripheral synovitis as its main manifestation. The presentation of the disease and the course during time are highly variable both within as well as between individuals.The symptoms and signs of RA may vary from joint complaints like pain, stiffness, swelling and functional impairment, to more constitutional complaints like fatigue and loss of general health. Because of this variety in disease expression a huge number of outcome variables have been used in the past decades to evaluate interventions in clinical trials.1

Many efforts have been taken in the past years to standardise the assessment of RA aiming at making study results interchangeable. Consensus has been reached about a minimal set of disease activity variables to be measured in clinical trials.2 ,3 As a following step response criteria based on these core set variables have been developed by the European League Against Rheumatism (EULAR),4 and the American College of Rheumatology (ACR).5 The recent introduction of new, very effective, antirheumatic agents has forced many researchers to modify these response criteria.6 ,7 The validity of several of them however is questionable and gives rise to as yet unsolved problems, which will be discussed in this paper.