Acquired activated protein C resistance, high tissue factor expression, and hyper-homocysteinemia in systemic lupus erythematosus.

Activated protein C resistance (APCR), high tissue factor (TF) expression, and hyper-homocysteinemia are associated with thromboembolic diseases. Thromboembolism is a frequent complication of systemic lupus erythematosus (SLE). In this study, we evaluated the prevalence of APCR, high TF, and homocysteine with correlation of the thrombotic tendency in SLE. Ninety-four SLE patients and 28 normal controls were included. APC ratio and TF antigen were measured using commercial kits. Plasma homocysteine level was measured using HPLC. The prevalence of APCR, high TF antigen level, and hyper-homocysteinemia in our SLE patients were 21.3%, 66.0%, and 23.4%, respectively. The median plasma level of TF antigen in SLE patients was 145.23 pg/mL (range, 31.00-778.50 pg/mL), which was significantly higher than the control value of 39.83 pg/mL (range, 1.55-168.50 pg/mL). The median APC ratio in SLE patients was 2.76 (range, 1.48-13.47), which was significantly lower than the control value of 3.59 (range, 0.26-5.66). The plasma level of homocysteine was not significantly different from that of control. A significant association was observed between the presence of APCR (OR = 8.59, P < 0.0001) but not with the presence of high plasma TF antigen level (OR = 1.24, P = 0.67) and thrombotic complications in SLE patients. In conclusion, APCR and high plasma TF levels are common in SLE, but a significant association was observed only between the presence of APCR and thrombosis in SLE patients. Copyright 2003 Wiley-Liss, Inc.