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 spoken as “ZAP” and not the more commonly used “Z-ZAP.”

Ok, now to what it is: 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.

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