[Evaluation of the kinetics of hemagglutination using a simple photometric technic]

A photometric technique to evaluate haemagglutination kinetic is presented in this paper. The technique applies the relative optical extinction (EO) produced on a light beam transmitted through a suspension of small particles (red blood cells and their agglutinates). The optical extinction decreases as the red cell agglutinates grow, giving a parametric estimate of the haemagglutination rate. Hence, optical extinction can be used to distinguish erythrocyte subgroups characterized by the differences appearing in the number of antigenic sites per cell. The paper describes the technique and gives the results of a set of experiments carried out on 90 samples constituted by 30 samples of A1 adults, 30 samples of non-A1 A adults and 30 samples of A newborns (cord red blood cells). Results show significative differences between subgroups. Parametric values such as the total relative optical extinction reduction (difference between the initial and the final values of EO) and the initial optical extinction rate are analyzed. Results from A newborn red cells show similar behaviour as the non-A1 A adult red cells and significative differences from A1 adult red cells. A correlation between parametric values and the number of antigenic sites per cell, as found in the literature, becomes evident.