Contribution of the monocyte to thrombotic potential.

The circulating monocyte exhibits the capacity to initiate and accelerate the coagulation cascade. We have devised a simple whole blood clotting assay which quantitates the monocyte's contribution of procoagulant (a marker of monocyte activation) to the clotting process and in addition, measures the in vivo activation of the cell. Citrated whole blood is added to saline and the recalcification time (RT) determined without incubation (RT control), with two hours incubation (RT saline), or added to endotoxin with incubation (RT endotoxin). The reduction in value between RT control and RT saline is a measure of monocyte activation in vivo. The reduction in time between RT saline and RT endotoxin is a marker of monocyte activation in vitro. This simple test enables the measurement of monocyte activation and this cells contribution to the hypercoagulability described in many disease states.