Study of red blood cell aggregation by admittance measurements

A method based on dielectric properties of cellular suspensions was developed to study red blood cell (RBC) aggregability, The time-dependent current in a Couette-type viscometer was recorded after abrupt stoppage of shearing, Since the current reaches steady state 2 min after the end of shearing, the observed effects were quantified by the relative current difference, Delta I-rel = (I-2min-I-5s)/I-2min, where subscripts designate the time of measurements, Delta I-rel increases with hematocrit, plasma and fibrinogen concentration, The dependence of Delta I-rel and of RBC aggregability on the concentration of dextran were similar. The experimental data and their analysis indicate that in suspensions with aggregating media, the Delta I-rel value measured in the field of the beta-dispersion reflects the difference between the size of aggregates under steady-state conditions and that of dispersed particles 5 s after the end of shearing. Therefore, this value may serve as a measure of RBC aggregability.