Autoantibodies to human prothrombin and clinical manifestations in 207 patients with systemic lupus erythematosus

Prothrombin (factor II) is one of the phospholipid binding proteins with a procoagulant property. Some publications have shown the presence of autoantibodies against prothrombin (aPT) in patients with antiphospholipid antibodies (aPL). We assessed the clinical significance of aPT in thrombotic events in patients with systemic lupus erythematosus (SLE).

IgG and IgM aPT were tested by ELISA in 207 patients with SLE.

Fifty-eight patients (28%) had positive aPT (> mean + 3 SD of 100 controls). Twenty-eight (14%) had IgG alone, 21 (10%) IgM alone, and 9 (4%) had both IgG and IgM. Patients with aPT had a history of thrombosis more frequently than those without aPT [31/58 (53%) vs 47/149 (32%), chi-squared=7.6, p=0.006]. No correlation was found between the presence of aPT and clinical features of SLE.

aPT are frequently found in patients with SLE, and are a potential marker for thrombosis.