Blood Group Typing by Ultrasound Backscattering—quantitative Measurements of Agglutinates and Their Shear-Dependent Behavior

A new method is presented to investigate the agglutination of red blood cells (RBC). In the present work, ultrasound backscattering was used to study erythrocyte suspensions prior to, and after, the reaction with blood group-specific antibodies. Scatter values allow for determination of the agglutination strength as well as for assessing the effect of external factors, such as shear stress, on the agglutination equilibrium. Based on the statistically significant increase of scattering values obtained from the test samples (when compared to the control samples), the blood group characteristics M, N, A1, AB, D and C could be determined reliably. It was demonstrated that a method is capable of providing quantitative data about the agglutination. It was possible to detect very small particles at an early stage of agglutination. Furthermore, the effect of shear stress on the agglutination equilibrium of RBC was estimated. Higher scatter values observed within the 50 s−1 to 170 s−1 range of shear level is interpreted as a strengthening of the agglutination resulting from the increase of shear stress. A decrease in agglutination was observed in all samples when shear levels exceeded 170 s−1. This effect was reached after anti-M and anti-N reaction, as well as after anti-A or anti-B reaction. Under conditions of increasing shear, control samples without added antibody or glutardialdehyde (GDA)-hardened RBC (with antibody treatment) exhibit no significant change in scatter values.