Abstract
The platelet aggregability can be numerically evaluated, when one can determine the minimum dose of ADP necessary for developing the secondary aggregation of platelet-rich plasma. In this report, we propose the procedure of determining the critical ADP level by means of comparing the aggregation patterns with a set of standard patterns stored in a computer. The estimated ADP threshold level is then converted into an aggregation index PAT (platelet aggregability index), which enables us to grasp the increased platelet aggregability in a patient, as a risk factor of the cerebral ischemia.