Clinical significance of acquired activated protein C resistance in patients with systemic lupus erythematosus.

Antiphospholipid antibodies (aPL) may induce acquired activated protein C resistance (acquired APCR). The role of acquired APCR in patients with systemic lupus erythematosus (SLE) is not well known. To evaluate the prevalence of acquired APCR and its association with clinical manifestations we studied 103 consecutive SLE patients and 103 matched controls. APCR in the undiluted test and after dilution in factor V deficient plasma, factor V Leiden, protein C and S, lupus anticoagulant, and anti-cardiolipin, anti-beta2-glycoprotein I and anti-prothrombin antibodies were determined. Factor V Leiden was found in 4% in both patients and controls. The prevalence of acquired APCR was 22% for the undiluted assay and 17% in the diluted test. In SLE patients, acquired APCR was associated with aPL (39 vs 13% in undiluted assay, P = 0.007; and 33 vs 7% in the diluted test, P = 0.001). Arterial thromboses were found in 24% of patients with acquired APCR and in 6% of patients without (P = 0.04). However, no relationship was found with venous thrombosis. Acquired APCR was also associated with pregnancy losses: miscarriages in 70% of women with acquired APCR vs 32% in those without (P=0.03). Thus, in SLE patients acquired APCR seems to be associated with increased prevalence of arterial thrombosis and pregnancy losses.