Abnormalities in the protein C anticoagulant pathway detected by a novel assay using human thrombomodulin

We developed a novel assay using human thrombomodulin (TM), which detected overall abnormalities in the protein C anticoagulant pathway (PC pathway). This assay indicates the degree of inhibition of prothrombinase by TM, which is represented as the percentage of prothrombinase inhibition by 25 ng/ml of TM, termed PIP25 (Prothrombinase Inhibition Percentage). We examined PIP25 in plasma samples from patients with systemic lupus erythematosus (SLE) with or without lupus anticoagulant (LA), patients with Behcet's disease (BD), and patients with miscellaneous thrombotic vasculitis and compared these with the PIP25 of plasma samples from healthy volunteers in Japan. The PIP25S were significantly lower in SLE alone (35.5 +/- 12.8%, P = 0.036) and SLE with LA (33.0 +/- 13.3%, P = 0.030) and BD (33.3 +/- 13.4%, P = 0.010) than those in healthy volunteers (43.5 +/- 10.7%). There was no significance between healthy PIP25 and those with miscellaneous thrombotic vasculitis (44.2 +/- 8.4%, P = 0.823). These results suggest that the abnormalities of the protein C anticoagulant pathway were present in patients with SLE(LA) and BD.