Increased TF PCA in intact cellular fractions in SCD. Platelet-depleted cell fractions were isolated by centifugation from heparin-anticoagulated whole blood. PCA was measured on these washed intact (non–freeze-thawed) cell fractions using a two-stage assay as described in Patients and Methods. P < .0005 for control versus LPS-treated controls; P < .000001 for control versus SCD.