Measurement of red blood cell aggregation in a "plate-plate" shearing system by analysis of light transmission.

The analysis of light reflection from or transmission through a blood sample under defined shearing conditions is widely used to assess red blood cell (RBC) aggregation. Different shearing geometries have been used to generate a constant shear rate within the blood sample, including "cone on plate" and Couette systems. In this study, a rotating glass plate, together with a parallel stationary plate, was used to generate a given shear rate at the point of light transmission measurement. The system gave reproducible results and proved to be sensitive to alterations in RBC aggregation. A comparison between different RBC aggregation parameters that can be calculated using the same light transmission curves (syllectograms) was also made. The index calculated by integrating the area under the syllectogram (M index) was found to be the most appropriate aggregation parameter to be used for comparisons between two groups of blood samples with different aggregation characteristics.