Radiographic hand joint space width assessed by computer is a sensitive measure of change in early rheumatoid arthritis

Objective. To compare changes in the computerized measurement of radiographic hand joint space width (JSW) to changes in modified Sharp scores in a retrospective 2-year study of early rheumatoid arthritis (RA). Methods. First and last standard clinical hand radiographs of 245 patients with RA were analyzed blind using purpose-written computer software to measure changes in JSW for proximal inter-phalangeal (PIP) and metacarpophalangeal (MCP) joints in the 3 middle fingers of each hand. Before measurement, the radiographs were scored independently by 2 radiologists using a modification of Sharp scoring. Results. The paired changes in JSW (-0.051 +/- 0.005 min) and Sharp score (+3.81 +/- 0.50) were both significant over the study duration. In measured joints showing an increase in joint space narrowing (JSN) score, 92% had a corresponding reduction in JSW. In patients with an increase in total score, including JSN and erosion scores in fingers and wrists, 84% had a corresponding reduction in mean (PIP + MCP) JSW. Patients with no change in Sharp score (47%) still experienced a significant reduction in measured JSW (-0.027 +/- 0.006 mm). HLA-DR genetic markers of severe disease progression were associated with significantly greater reductions in JSW but not increases in Sharp score. (Values: mean standard error of mean). Conclusion. Measured JSW averaged over 6 PIP and 6 MCP joints was a valid and more sensitive measure of change than total Sharp score in this study of early RA.