Opposite changes in aggregability of platelets stored in plasma and in blood

The effect of storage on the aggregability of platelets in plasma and in whole blood was studied with blood samples obtained from 11 normal subjects. Compared to aggregation of platelets in fresh samples, those stored in plasma showed an increase in aggregation, and in whole blood a decrease in aggregation. The decreased aggregation in the latter samples was prevented by including exogenous glucose in stored blood samples. Similar studies were performed on 25 patient platelet samples that had been judged as hyperaggregable by standard procedure, including the presence of "spontaneous" aggretation in 13 specimens. Only seven samples prepared from stored blood still showed hyperaggregability; spontaneous aggregation remained in only five samples.