Determination of specific red blood cell aggregation indices via an automated system

Abstract

Although red blood cell (RBC) aggregation remains an important issue in hemorheology, measurements of specific aggregation parameters are not usually performed routinely in many laboratories; this is primarily due to the present lack of appropriate instrumentation. We have thus developed an automated and interactive system, based on light transmission measurements using a modified Myrenne Aggregometer and a laboratory computer, which provides rapid and routine determination of seven RBC aggregation indices. The computerized system allows control of shear rate as well as recording and analysis of digitized light transmission data. Aggregation indices measured with this system include: 1) extent of aggregation at stasis (AI, AMP); 2) kinetics of aggregate formation (T_1/2, T_FAST, T_SLOW); 3) shear resistance of RBC aggregates (Y_Tmin); 4) aggregate formation induced by low shear (FSAR). Results obtained for RBC/plasma suspensions indicated appropriate reproducibility, several cross-correlations between the indices (except between AI versus T_FAST or T_SLOW), that fibrinogen affected all indices, and that donor age markedly influences aggregation behavior. Dextran suspending media demonstrated the expected biphasic aggregation response of this polymer. RBC modified by heat treatment or by shape altering agents exhibited changes versus control, and age fractionated red cells demonstrated marked differences in aggregation behavior. In overview, the results indicate the necessity to determine more than one parameter to fully describe the aggregation process, and suggest the usefulness of this newly developed system for both routine clinical studies and basic research investigations.