Because the serum/plasma is reacting with all cells tested, a method must be employed to remove the autoantibody causing the broad reactivity while not removing the potential alloantibody(ies) that still need to be identified. One method to determine if alloantibody is demonstrable in the presence of autoantibody is autoadsorption.
The use of an enzyme or ZZAP-treated autologous cells facilitates the removal of autoantibody by removing membrane structures that interfere with antibody binding. Note that the presence of donor cells in the patient's circulation may result in unreliable findings with either cold or warm autoadsorptions. Therefore, autologous adsorptions cannot be accurately performed if the patient has been transfused within the past three months.
More than one adsorption may be needed, depending on the strength of the autoantibody. Testing the adsorbed serum with DAT-negative (treated) patient cells is a good way to determine if all the autoantibody has been removed.