Quantitative measures and indices to assess rheumatoid arthritis in clinical trials and clinical care

Quantitative measures that are used to assess the status of patients who have rheumatoid arthritis (RA) may be classified broadly as measures of disease activity, measures of damage to joints and other organs, questionnaire and physical measures that are sensitive to activity and damage, and long-term outcomes (Table 1) [1]. Measures of disease activity, such as joint swelling, are consequences of a dysregulation that leads to inappropriate production of cytokines; this is analogous to elevation of glucose in diabetes and of blood pressure in hypertension. Abnormalities that are indicated by these measures are reversible and are not intrinsically harmful, unless they lead to organ damage. Generally, unchecked dysregulation leads to long-term damage if no effective therapy is instituted [2,3]. Measures of damage, such as radiographic progression and joint deformity, tend to be medically irreversible. Questionnaire and observer-derived measures of physical function, pain, and global status reflect activity and damage because they are affected by reversible and irreversible phenomena. Self-report of functional status also reflects underlying psychologic factors that are not a direct result of disease activity or damage. Nevertheless, patient questionnaires identify and predict the most costly consequence of RA-work disability [4-6]-and other severe long-term outcomes, such as functional declines [7,8], costs [9], and.