Coagulation Tests and Platelet Economy in Atherosclerotic and Control Subjects

Blood coagulation was studied in 31 atherosclerotic male subjects and in 44 control male subjects. The mean platelet adhesive index was significantly greater in the atherosclerotic group and the plasma thromboplastin time was significantly shorter. These two tests are measures of the activity of the early stages of coagulation. The other in vitro tests of coagulation showed no significant differences. At present, platelet consumption is probably the only available measure of the activity of the early stages of coagulation in vivo. Platelet survival and daily turnover was accordingly determined with DFP 32 . Mean platelet survival was shorter and mean platelet turnover was greater in the atherosclerotic group. Division of the groups according to family history of atherosclerosis proved important. The most clearly separated groups were the atherosclerotic group with a positive history and the controls with a negative history. The remaining two subgroups are much more alike. This was true of both in vitro and in vivo tests. Despite the high experimental error, the in vivo tests correlate well with the in vitro tests of the early stages of clotting though poorly with tests of the later stages. It is concluded that differences exist between atherosclerotic and control subjects in the early stages of coagulation, and that in vitro tests are satisfactory indices of this difference. In their present form, none of these tests is suitable for diagnostic or prognostic purposes in the individual.