Validity of the Wu-Hoak method for the quantitative determination of platelet aggregation in vivo

Summary Quantitative determinations of platelet aggregation were made by a modified version of the Wu-Hoak-method in venous blood samples from ten healthy volunteers. It was demonstrated that the extent to which aggregates are formed depends on the rate of flow in the needle and on other methodical influences as well as on the platelet count. Accordingly, no definite conclusions concerning aggregation conditions in vivo can be drawn from the results obtained with venous blood samples.The authors wish to thank Mr. A. Ehrengruber for performing the statistical calculations.