A biological approach to the platelet survival curve with criticism of previous interpretations.

The biological mechanisms of platelet destruction must be correctly identified before platelet survival curves can be interpreted. This report develops a theory of platelet destruction which is compared with experiments performed on platelets labelled with the radioactive isotope 51Cr. Platelet destruction rate is a complicated function of platelet number and the thrombokinetic destruction state of the body. A linear approximation of this function shows that destruction is dominated by constant and random consumption. A second order non-linear approximation shows the effect of 'platelet crowding'. This theoretical study explains the difference between predicting the complete platelet survival curve from only two experimental points (in the linear approximation) and the methods of curve fitting currently recommended by the International Committee for Standardization in Haematology. It indicates that the curve fitting of known functional forms to experimental data usually results in an under interpretation of the observations and dilutes the diagnostic potential of the platelet survival curve.