Alloadsorption (differential adsorption) can be used if the volume of the patient’s red cells for testing is limited, if the patient has been transfused within the last three months or if autoadsorption fails to remove the autoantibody.
Cells must be carefully selected to include all clinically significant blood groups.
In general, at least three papain-treated cells (R1R1, R2R2and rr) which are each individually negative for K, k, Jka, Jkb, Fya, Fyb, S and s, are individually incubated with the patient’s serum. This is repeated until the autoantibody is adsorbed out. The samples are centrifuged and the supernatant used for testing against panel cells. Each of the three sets of adsorbed serum must be tested against the panel cells, and each must be tested separately against donor cells by IAT at 37°C.
Note that adsorptions may result in weakened alloantibody reactivity.
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