A new index for collagen induced platelet aggregation

In this paper, we propose a new index of platelet aggregation for optical aggregometry, the "R" value. This represents the rate of change in the half time for platelet aggregation (T1/2) induced by collagen with changes in the platelet concentration and expresses the degree of platelet sensitivity to collagen. The "R" value has been shown to reflect the aggregability of platelets due to activation of the contact factors. The "R" values were significantly different in the acute and chronic phases of occlusive arterial disease, while ordinary platelet aggregation parameters did not change. A decrease in the "R" value appears to indicate a platelet hyperfunction and hypercoagulable state, in other words a prethrombotic state.