The assessment of disability: from first to future principles.

Outcome assessment attempts to measure the long-term impacts of illness in order to select management strategies and public policies which minimize these impacts. Disability is an important dimension of outcome, particularly in conditions such as rheumatoid arthritis, but cannot be considered apart from other dimensions such as mortality, pain, iatrogenic problems, and economic impact since decisions frequently involve comparing positive effects in one dimension with negative effects in another. Modern techniques of survey research have yielded self-administered patient questionnaire instruments which are more reliable and more valid than traditional endpoints in rheumatic disease assessment and more relevant to the desires of the patient. These new techniques should be widely used in clinical investigation and in clinical practice.