Objectives We investigated the serum levels of soluble intercellular adhesion molecule-1 (sICAM-1) and the activity of erythrocyte superoxide dismutase (SOD) in rheumatoid arthritis (RA). We also sought whether there was a correlation between sICAM-1 and erythrocyte SOD and whether the levels of sICAM-1 reflected disease activity.

Methods Levels of sICAM-1 were measured in serum of 42 patients with active RA and 30 control subjects by an enzyme-linked immunosorbant assay. SOD activity was determined in erythrocytes isolated from patients with active RA and from controls.

Results The serum levels of sICAM-1 were significantly higher in the patients with RA than in the control subjects (p < 0.001). In contrast, the activities of erythrocyte SOD were significantly lower in RA patients than those in healthy controls (p < 0.001). A significant negative correlation was found between the levels of sICAM-1 and erythrocyte SOD activity (r = ?0.39, p < 0.01). There was a statistically significant positive correlation between sICAM-1 levels with Ritchie articular index (RAI) score and C-reactive protein (CRP) (r = 0.32, p < 0.05; r = 0.44, p < 0.01, respectively), whereas no significant correlation was observed between sICAM-1 and erythrocyte sedimentation rate (ESR) (r = 0.21, p > 0.05).

Conclusion These results show that the increased levels of sICAM-1 present in active RA patients might be due to the decreased activity of erythrocyte SOD, and increased levels of sICAM-1 may also reflect disease status or activity.