Assessment of disease activity

The concept of disease activity is useful for characterizing chronic rheumatic diseases and their current degree of severity. Disease activity should be clearly differentiated from damage, which is irreversible. A number of requirements must be met in order to make a measure of disease activity acceptable and valid. Methods for measurement have been developed in the areas of biological, radiographic, ultrasound and computerized imaging techniques. Recently, a particular effort has been made to develop questionnaires in the form of complex indices, derived from the observations of physicians, and self-report questionnaires for patients. Such assessments of disease activity are available for most of the chronic inflammatory rheumatic diseases. They are particularly relevant at a time when new biological drug therapy is being developed. Research effort is needed to develop more instruments suitable for use in clinical practice for individual patients.