Quantitative changes in platelet aggregation due to physiological and pathological factors and medication.

Quantitative measurements of platelet aggregation in samples of venous blood were made in altogether 66 healthy volunteers by a modified version of the method of Wu and Hoak. The formation of aggregates was found to be unaffected or at the most barely affected by such factors as sex, age, smoking, fatty food, physical exertion and medication with isoprenaline or ovulation inhibitors. No difference in the number of aggregates formed was noted between 12 control patients and 16 patients with myocardial infarcts or 14 with other conditions predisposing to arterial thrombosis. Anticoagulant therapy had no effect on aggregation. It is suspected that aggregation in vitro due to methodological factors may obscure any quantitative alterations in the formation of aggregation present in vivo.