“Adsorbed serum” or “adsorbed plasma” simply refers to the serum or plasma “left behind” after an adsorption is done (note that the term “adsorbed plasma” refers to a sample is anticoagulated; i.e., adsorbed serum applies when the original sample is in a red-top tube of clotted blood, while adsorbed plasma applies when the sample is in a purple-top tube of unclotted, or “anticoagulated” blood).
This is a confusing term to people that are learning blood banking. When we perform an adsorption, the intent is to use specific red blood cells to bind specific antibodies from the patient’s serum to the RBCs. Then, we centrifuge and separate the RBCs that are coated with the target antibody away from the serum, leaving any other antibodies in that serum behind. We call the “left behind” serum or plasma adsorbed because that term describes what has been done to it.
This process is most commonly done as an autoadsorption, meaning we use the patient’s own RBCs to bind up autoantibodies, leaving behind antibodies against other people’s RBCs (aka, alloantibodies) in the adsorbed serum. The antibodies that do not bind (in the adsorbed serum or plasma) can then be analyzed and identified. I discuss this further in the entry for autoadsorption.
I’ve discussed this elsewhere, but the most common mistake people make with this term is calling it “aBsorbed” rather than “aDsorbed.” The terms have two different meanings; see the link in the first sentence above for the distinction.
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