The liquid portion of a specimen collected in a tube containing ethylenediaminetetraacetic acid (EDTA) is serum.

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The liquid portion of a specimen collected in a tube containing EDTA is actually plasma, not serum. EDTA is a common anticoagulant that prevents blood from clotting by binding calcium ions, which are necessary for the coagulation process. When blood is collected in an EDTA tube and centrifuged, the resulting liquid portion is plasma, as it still contains all the clotting factors and other blood proteins that would normally be present in whole blood. Serum, on the other hand, is the liquid portion of clotted blood that has had those proteins removed by the clotting process. So, although EDTA is often used in blood collection to produce anticoagulated specimens, the resulting liquid portion is not serum.

The Liquid Portion of a Specimen Collected in a Tube