An improved technique for the electronic measurement of platelet size and shape.

A method is described for the rapid and accurate measurement of platelet size utilizing the Coulter Counter model ZB and Channelyzer C-1000. A simple hydrodynamic focusing apparatus and a special aperture tube were used to improve the accuracy of the system. By collecting samples both in EDTA and citrate, measurements could be based directly on stable and linear calibration data derived from latex spheres. Since the platelet size distribution conformed well to a log-normal model, distribution parameters were calculated on this basis. Utilizing samples from normal individuals, platelets collected in EDTA appeared spherical and had a mean volume of 9.0 mu3. Platelets collected in citrate appeared discoid and had a mean volume of 7.3 mu3 (uncorrected for shape). An EDTA/citrate ratio of 1.26 was calculated from the median platelet volumes. A thrombocrit was determined by multiplying the mean EDTA platelet volume by the total platelet count. In normal individuals the thrombocrit ranged from 0.18 to 0.34 per cent.