Evaluation of red blood cell aggregation in diabetes by computarized imageanalysis

Red blood cell (RBC) aggregation has been widely studied and its importance is well established in the rheology of microcirculation. RBC aggregation i s a major factor responsible for the flow properties of blood. Increased RB C aggregation has been observed in several pathological states. Therefore, the measurement of erythrocyte aggregation is theologically important for q uantifying flow abnormality in pathological conditions. Normal RBC under lo w flow or at rest form rouleaux aggregates, while abnormal RBC aggregation may lead to the formation of irregular aggregate structures, which may be i nduced by cell-associated factors (reduced membrane sialic acid levels) but also by extracellular factors. The main objective of the present investiga tion was to study RBC aggregate morphology in diabetic patients, using dire ct microscopic observation and numerical processing of recorded digitized i mages. Blood samples were obtained from 20 diabetic patients and from 15 no rmal control subjects. The aggregate morphology was quantified by the so-ca lled Aggregate Shape Parameter (ASP) defined as the ratio of the aggregate projected area to its square perimeter. ASP appeared significantly higher ( p < 10(5)) in diabetic patients (0.65 +/- 0.18) than in normal controls (0. 28 +/- 0.15). This rheo-optical method based on the theoretical model for r ouleaux aggregates provides a useful reference for measuring deviations of RBC aggregate morphology. Increased aggregation of RBC resulting from a dec reased sialylation of glycophorins may be an important factor in the develo pment of vascular diseases and in the microcirculation impairment.