Acronym for “Rabbit Erythrocyte Stroma,” which is a commercial product used by some blood bankers to remove (or “adsorb“) cold antibodies from a patient’s blood sample. These antibodies are usually autoantibodies) that have specificity to the “I” or “IH” antigens. Cold antibodies are generally clinically insignificant, but they certainly can cause problems for laboratories that are trying to perform ABO and Rh testing, as well as crossmatching the patient’s blood for transfusion. Blood bankers have known for over 30 years that treated rabbit erythrocytes remove IgM cold antibodies from samples, allowing the workers to then test the “adsorbed serum” and find the patient’s true ABO/Rh type and get a more accurate compatibility test. RESt is simply a commercial extension of that principle. The problem, as outlined in several articles over the last few years, is that RESt can also adsorb clinically significant antibodies that are primarily IgM, as demonstrated with anti-Vel most clearly, but also shown with many other significant antibodies with an IgM component (most notably, anti-B). As a result, laboratories can also use other techniques to also take these antibodies out of play, most commonly including using “pre-warming” (incubating all reagents and test serum to body temperature before mixing them). Since the cold antibodies, by definition, react best below body temperature, pre-warming changes the conditions to ones in which the cold antibodies may not react at all. Unfortunately, pre-warming may also mask the presence of significant antibodies, so neither solution is perfect. RESt remains a useful tool in the immunohematology reference laboratory arsenal.

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