[The hemorheological laboratory in clinical medicine: the value and limitations of its methods].

Hemorheology has been a part of clinical research since precise parameters were determined for the study of flow properties of the blood. A laboratory for clinical hemorheology is nowadays equipped with a variety of instruments, ranging from highly sophisticated to very simple ones, to be used for the measurement of blood viscosity and its main components. The extremely precise viscometers now available for this purpose allow us to take measurements at different shear-rates and can function with small volumes at controlled temperature. The study of blood viscosity goes along with that of its main determinants. Among these there are to be reckoned plasma and serum viscosity, with its main components, i.e. proteins and fibrinogen, and also corpuscular viscosity, i.e. hematocrit and leukocrit. Special consideration is deserved by the methods attempting to evaluate the deformability and the aggregability of the erythrocytes which are, at present, matters of great interest. As far as the deformability of the erythrocytes is concerned, it is to be pointed out how different is the concept of deformability from that of filterability, and how methods directed to the study of the whole blood differ in their significance from those concerning washed red cells. Furthermore, it is to be emphasized that every method has its own questionable points. This is the case also of the methods studying the aggregability of the erythrocytes, a very complex phenomenon which for the time being seems quite difficult to evaluate.