Erythrocyte aggregation: experimental approaches and clinical implications.

From a clinical point of view, quantitative studies of erythrocyte aggregation or rouleau formation is of great interest. However, in order to approach the phenomenon, structural parameters (rouleau shape), kinetic parameters (rouleau formation and dissociation velocity) and rheological parameters (dissociation thresholds) must be determined. At present, optical dynamic methods are available for use in clinical hemorheology. They involve optical measurements in a viscometer. The first method consists of a study of the light intensity transmitted through the measuring chamber of a cone plan viscometer. A device calculates and index I, which provides a whole approach to the aggregation kinetics. On the other hand, a systemic which also involves a cone-plain viscometer and an inverted microscope (Rheoscope) allows to collect data by means of microphotographs, microcinematography or numerical image processing. In that case, an adimensional K index typical of the morphology of the aggregates can be determined. The second method involves the analysis of the light intensity backscattered by the red blood cells sheared in a Couette flow. An automatic system has been developed and aggregation times, orientation and structure index, total and partial disaggregation thresholds can be determined on the basis of the curves of variations of backscattered light.