The patient’s platelet-derived FV pool remaining 10 days after plasma administration supports thrombin generation in a TF-initiated whole blood clotting model. Whole blood from the patient was incubated (at 37°C with rocking) with TF (5 pM) alone (closed squares), TF (5 pM) plus PAR1 (100 μM) and PAR4 (500 μM) agonist peptides (closed circles), or TF (5 pM) plus FV (2 nM) (open circles). TAT formation was measured by ELISA as described in “Study design.” For comparison, TAT formation in the presence of PAR agonist peptides was also assessed in 2 unaffected individuals assayed in duplicate (mean ± standard deviation) (open triangles).