I must be missing something. Slide 48 lists that the zeta potential is inversely proportional to the ionic strength of the medium and density of the ionic cloud. That would mean that a low-ionic strength solution (LISS) increases zeta potential. Since the zeta potential is basically an indicator of electrostatic repulsion between similarly charged particles, that would mean that LISS would increase the electrostatic repulsion between RBCs, which, I believe, is not the case.
I guess I'll have to go back and brush up on my chemistry.
Just out of curiosity, do you test papain- or ficin- treated cells when working up cold agglutinins?