The validity of radiography as outcome measure in rheumatoid arthritis

Radiographic imaging of hand (and foot) joints is regarded as one of the gold standards of outcome for rheumatoid arthritis. Outcome can be defined as suffering or loss of health caused by the disease process, and process as the abnormal physiological consequences that follow from the cause of the disease. By these definitions and through a review of validity components, I propose that radiographic damage may be best viewed as a unique and important measure of past process, and possibly as a proxy for outcome.