Electronic platelet counting after isopycnic differential centrifugation a simple rapid and accurate method

A semi-automatized platelet counting procedure with the use of a Coulter Counter is described. Its originality consists in providing an electronic method of counting of the platelets after a differential centrifugation of the blood sample previously diluted with a hypertonic NaCl solution (density 1.053) which is isopycnic to platelet density. This procedure allows elimination of red and white cells without loss of platelets in the supernatant. The final platelet number can be calculated without further corrections. The method is quick and does not require specially skilled technicians. A single technician can perform 40 counts in one hour. The reproductibility of the method is excellent and the coefficient of variation 2,4%. The accuracy and feasibility of the method is also sustained by two years' experience in an haematological routine laboratory.