Warm-Reactive Autoantibodies - Investigation:

Once a warm autoantibody has been established, the next step is to exclude the presence of any underlying alloantibodies. This can be a difficult process as the pan-reactivity from the autoantibody can mask alloantibodies in routine investigations. Obtaining a thorough transfusion and pregnancy history is critical, as a nulliparous non-transfused patient is unlikely to have any exposures that could stimulate RBC alloantibody production.

It is also useful to look at the pattern of pan-reactivity, and whether the reactions are uniform (e.g. all 3+ or 4+). Differing reaction strengths may signal the presence of an underlying alloantibody. The difference in reaction strength between cells that are and are not incompatible for an underlying alloantibody can also be brought out by diluting the patient plasma before testing, or by moving from gel column or solid phase testing to tube testing, which tends to be less sensitive.

The most definitive method for ruling out the presence of a masked alloantibody, however, is to remove the interference of the panagglutinating autoantibody. This is accomplished through adsorption studies, which can be either performed using the patient’s own cells (i.e. autoadsorption) or with carefully selected panel cells (i.e. alloadsorption).

Next page: Autoadsorption

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