Plasmas collected in the absence of CTI show few significant differences in clotting between FXI-deficient nonbleeders and bleeders. Plasmas from healthy individuals and FXI-deficient patients that were not collected in the presence of CTI were clotted by recalcification and addition of tissue factor and phospholipids. Clot formation was monitored by turbidity. (A) Onset time, (B) rate (Vmax), (C) time to plateau, and (D) peak turbidity change for controls, all FXI-deficient patients, 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.