Fibrinolysis assays performed with CTI-treated plasmas differentiate FXI-deficient bleeders from nonbleeders. Clotting was triggered in CTI-treated plasmas from healthy individuals and FXI-deficient patients by recalcification and addition of tissue factor, phospholipids, and tissue plasminogen activator. Clot formation and lysis were monitored as an increase and subsequent decrease in turbidity. (A) Onset time, (B) rate (Vmax), (C) time to peak turbidity, (D) peak turbidity change, (E) area under the curve, and (F) lysis time for controls, all FXI-deficient, and only FXI-deficient patients with partial deficiency (16-60 IU/dL). Symbols represent plasmas from individual subjects; lines show median and interquartile range. *P < .05, **P < .005.