Elevated FVIII increases thrombin generation in an in vitro model of mild, but not severe, TF (SMC) exposure. Recalcified (16mM, final) human NPP spiked with FVIII or HBS (20mM HEPES pH 7.4, 150mM NaCl) was added to SMC monolayers of varying densities. Thrombin generation was measured by calibrated automated thrombography, as described previously.^22,33  (A-C) Thrombin generation curves representative of 5 independent experiments with SMC at 100% (A), 60% (B), and 20% (C) confluence. Symbols are 100% (open circles), 200% (closed circles), 300% (closed squares), and 400% (closed diamonds) FVIII, final. (D-F) Mean values (± SD) for lag (D), rate (E), and peak height (F) of thrombin generation for all 5 experiments with human NPP (1 U/mL FVIII) at different SMC confluence levels. *P < .05 versus indicated group. (G-I) Mean values (± SD) for the lag (G), rate (H), and peak height (I) of thrombin generation for all 5 experiments, at varying FVIII levels. *P < .05 versus 1 U/mL within each confluence level.