The relationship between serial measures of disease activity and outcome in rheumatoid arthritis

Disease activity was measured annually over a median period of 7 years (range 5–9) in a cohort of 127 patients with rheumatoid arthritis. The measurements were plotted, and the area under the resultant curve measured. The relationship of serial measures of disease activity (area under the curve) to outcome (measured radiologically, functionally and by global assessment) was investigated. A significant correlation was found between persistent disease activity and radiographic deterioration. Similar results were found for functional outcome, as measured by Steinbrocker grade, health assessment questionnaire score or global assessment (by analogue score). Single measures of disease activity did not predict outcome. Although imprecise, current methods of measuring disease activity in RA, if measured serially, are valuable in predicting outcome over a 5–10 year period.