Plasma levels of anti-tPA antibodies in patients with APS and controls. Anti-tPA antibody levels are expressed in units per milliliter; the horizontal lines represent geometric means. The results show that 91 APS patients had anti-tPA antibody levels higher than those in 91 healthy controls (P = .0001), 23 patients with SLE without antiphospholipid antibodies and APS symptoms (P = .0001), and 40 patients with antiphospholipid antibodies without APS symptoms (P = .05). Fourteen APS patients and 3 patients with antiphospholipid antibodies without APS symptoms had anti-tPA antibody levels higher than the 95th percentile of healthy controls (indicated by the dashed line).