Platelets in the prediction of thrombotic risk.

A study is reported which tries to identify those members of the general population who may be at increased risk of vascular disease. It is probable that patients who have had previous thrombotic episodes are inherently more at risk of further episodes and that a thrombus many months ago will not affect current tests. Accordingly we carried out a number of tests involving platelets on 'controls', and on patients with a past history of either myocardial infarction or deep vein thrombosis (DVT) and patients suffering from intermittent claudication who also are assumed to be at higher risk than the controls. Differences were demonstrated between controls and patient groups and these differences were utilized to develop statistical functions with the ability to discriminate between the groups. The functions were then tested using a second set of data from similar groups. Those designed to discriminate between myocardial infarction patients and controls and between patients with claudication and controls were validated. The heparin thrombin clotting time was found to be the prime predictor variable; the platelet count, platelet volume, platelet factor 3 clotting time and the bleeding time have some predictive value. The antithrombin clotting time, platelet aggregation and platelet adhesiveness tests as measured were not found to have discriminating potential. It is suggested that these appropriate risk functions could be of practical value in identifying members of the general population who may be at greater risk than average. The discriminate functions for DVT patients and controls could not be validated, suggesting differences in platelet involvement in arterial and venous thrombosis.