Serum thrombomodulin-a reliable marker of disease activity in systemic lupus erythematosus (SLE): advantage over established serological parameters to indicate disease activity.

To date no specific serological parameter is available to assess disease activity in SLE. Soluble serum thrombomodulin is a new marker of endothelial cell injury and vasculitis. The objective of this study was to compare in vivo soluble thrombomodulin as marker of disease activity in SLE with established and recent serological parameters. One hundred and twenty-four sera of 30 patients with proven SLE with different disease activities were tested for serum levels of thrombomodulin, intercellular adhesion molecule-1 (ICAM-1), E-selectin, vascular cell adhesion molecule-1 (VCAM-1), IL-2R, IL-6, IL-10, dsDNA by ELISA and dsDNA additionally by radioimmunoassay (RIA). C-reactive protein (CRP), complement component C3, IgG, creatinine, anti-nuclear antibodies (ANA) and intermediate filament antibodies were measured by standard laboratory tests. The clinical disease activity was evaluated by the Systemic Lupus Activity Measure (SLAM). Correlations of the different serological SLE disease activity parameters with the SLAM scores revealed the highest significance for serum thrombomodulin (correlation coefficient 0.82). This was further confirmed by the intra-individual analysis of follow-up sera. In addition, a moderate correlation could be found for IL-6, IL-10, ICAM-1, CRP and erythrocyte sedimentation rate (ESR). In summary, soluble thrombomodulin is the most important serological parameter of disease activity in SLE currently available, as shown by the in vivo studies. Soluble thrombomodulin might be a valuable serological parameter for therapeutical considerations.