ABSTRACT
Since, as discussed above, the term ‘outcomes’ is very wide, the focus of this chapter is to present the various disease activity measures that are commonly used. In this sense, we will rather take the perspective of the patient, the physician, or the trialist, and we do not focus on long-term consequences (the epidemiologist’s perspective). Therefore radiographic damage, which is a chapter on its own for these three diseases, will also not be discussed here. However, in some instances, the trade-off between the disease process and disease outcome is not always separable, as in the instance of measures of function, which can be used as surrogates of disease activity to follow patients in clinical practice,4 while they also partly represent a component that is related to the destructive consequences of the disease.5
