Serum Thrombomodulin in Myeloperoxidase-Antineutrophil Cytoplasmic Antibody (MPO-ANCA)-Associated Vasculitis.

Background and Aims : Although serum or plasma thrombomodulin (TM) was reported to be increased in various diseases with vascular injuries, blood TM was also shown to be influenced by renal function. In this study, we determined whether serum TM (sTM) could be a marker of vascular injury in patients with myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA)-associated vasculitis, in which kidneys are often affected. Methods : Thirteen patients with MPO-ANCA-associated vasculitis were investigated and 43 patients with chronic glomerulonephritis (CGN) served as a control. sTM was measured by one-step sandwich enzyme immunoassay method. Results : A significant positive correlation was found between sTM and serum creatinine (sCr) (sTM=2.24×sCr+2.16, r=0.91, P<0.001) in patients with CGN. In order to correct sTM for renal function, we calculated corrected sTM according to the following formula : corrected sTM (%)=[measured sTM/expected sTM at the measured sCr]×100=[sTM/(2.24×sCr+2.16)]×100. Patients with MPO-ANCA-associated vasculitis tended to have lower levels of corrected sTM before treatment compared to patients with CGN, but not significantly (86.8±23.2% vs. 98.7±18.3%, ANCA vs. CGN, P=0.12). Corrected sTM was increased significantly within 1 month after the beginning of treatment (145.7±46.9%, P=0.008, vs. before treatment in each patient). In remission, corrected sTM returned to the same levels of CGN (104.5±38.6%, P=0.03, vs. within 1 month in each patient). Conclusions : These results showed that sTM corrected for renal function does not simply reflect disease activity in MPO-ANCA-associated vasculitis.