Critical evaluation of platelet aggregation in whole human blood.

Platelet aggregation studies generally are performed in platelet-rich plasma (PRP) by the turbidometric method. The authors compared this technic with the recently introduced impedance aggregometry in PRP and whole blood (WB). In healthy controls there was a good correlation between the two technics when aggregation was induced by ADP or collagen. As compared with PRP, platelets in WB were more sensitive to the aggregating effect of thrombin, ristocetin, and arachidonic acid. Platelet sensitivity to prostacyclin was increased in WB. The anti-platelet effect of a single oral dose of aspirin could be detected for a longer period in WB than in PRP. Platelet aggregation tests in WB from patients with platelet dysfunctions showed the same response pattern to different aggregating agents as in PRP. In contrast to turbidometry, the impedance method in PRP and WB enabled registration of platelet aggregation in a dose-dependent fashion in a sample from a patient with severe hyperlipoproteinemia. It is concluded that platelet aggregation can be studied conveniently with the impedance method in the more physiologic medium of WB. Providing the same information as the well-established turbidometry, the time-sparing impedance method needs less citrated blood. Moreover, our results show an increased sensitivity of the WB system to some aggregating and anti-platelet agents.