Heterogeneity of human platelets. VI. Correlation of platelet function with platelet volume.

Platelet aggregation velocity was moosured with an aggregometer in plateletrich plasma from 34 normal subjects following addition of ADP, collagen, or epinephrine. Platelet volume parameters [mean, mode, megathrombocyte index (large platelets)] were determined with a model B Coulter Counter attached to a P64 Channel Analyzer with electronic recorder and correlated with platelet count. A negative linear relationship was found between platelet count and platelet volume (r = -0.53, p < 0.001). Platelet aggregation velocity induced with ADP, collagen, or epinephrine ( primary wave) was directly proportional to platelet volume and correlated best with megathrombocyte index: ADP, r = 0.62, p < 0.001; collagen, r = 0.59, p < 0.001; epinephnne, r = 0.53, p < 0.02. Platelet aggregation velocity induced with collagen or epinephrine correlated poorly with platelet moon or mode. Platelet aggregation velocity induced with ADP did not correlate with p1 atelet moon or mode volume (r = 0.27, p>O.l; r0.22, p>O.l, respectively). Platelet volume distribution curves of residual nonaggregated platelets revealed a relative absence of larger platelets. Thus, platelet aggregation velocity was propertional to platelet volume, but correlated best with the number of large platelets or megathrembocyte index, particularly with ADP-induced platelet aggregation. It is suggested that the clinical strategy for treatment of platelet disorders would be better directed toward evaluation of platelet size and function rather than number, and that experimental as well as therapeutic procedures for the harvesting of platelets be directed toward a method of collection in which a portion of the megathrombocyte population is not routinely discarded.