First things first: According to the inventor of this specialized blood bank reagent (Dr. Donald Branch, now with Canadian Blood Services, but at the time of invention at City of Hope in Southern California), it should be said like this: “ZAP” (not the more commonly used “ZEE-ZAP”). Hey, if you invent the thing, you get to decide how to pronounce it!
With that out of the way, what is it? ZZAP is a reagent composed of a mixture of a proteolytic enzyme (papain) and a sulfhydryl reagent (dithiothreitol, or “DTT“). It is used most often in immunohematology reference labs rather than hospital transfusion services, especially in workups for warm autoantibodies. ZZAP removes immunoglobulins and complement from the surface of DAT-positive red blood cells. ZZAP also deactivates a multitude of red cell antigens on the red cell surface. The most important antigens damaged/destroyed by ZZAP include all Kell antigens, M, N, and the two main Duffy antigens (Fya and Fyb), to name a few. Following treatment with ZZAP, red cells can be used for a variety of special techniques, such as adsorptions.
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