Since EDTA chelates calcium ions, and calcium ions are needed for the complement cascade and membrane attack complex to progress to hemolysis, should we discontinue using hemolysis as an endpoint when using EDTA anticoagulated blood for tube testing? (Our old (clot tube) SOP's say, observe for hemolysis and/or agglutination, but they also say "serum" not "plasma".)

I would agree that haemolysis is no longer a sign of a positive antibody reaction when using EDTA anticoagulated blood, but haemolysis in the actual draw tube is quite a useful indicator that a "cold" autoantibody is present (assuming of course that the phlebotomist has not used a blunt carving knife to draw the blood). In the "old days" we used to be quite precious about the presence of a little "pinkness" in clotted samples in case we missed antibody/complement-induced haemolysis, but, I must admit that, these days, I tend to disregard quite frank haemolysis in EDTA samples because, as you say, Ca++ (and, come to that, Mn++ and Mg++, which are also required and also chelated) is not available for the classic complement pathway.

In a way, it is a pity, because, with antibodies directed against high-frequency antigens, if there was haemolysis, it pointed to anti-I, anti-PPkP1, anti-H or anti-Vel (which was a great help). Shame; can't do this any more!!!!!!!!

:cries::cries:

Our pink and purple tubes are both the same size ( 6 mL ) but- we switched to the pink top for the BDID PIK (patient identification check) because it is notched and has a barcode on it-both K2 EDTA 10.8 mg

We've used pink tops for about 10+ years with very few problems - although K3 EDTA in biovue can sometimes give positive auto (roughly 1+) with negative DAT in BioVue cards. With grouping in cards no problem, although question - when your techs are doing the group, are you talking in tubes and are they chintzy with their antisera? i.e., do they use two drops or one? Because I think a one vol to one vol can give the "graininess" they're describing (but it's easily (and gently!) shook out - it doesn't look like agglutination).

We use pink top tubes for gel of course. When we first started using them there was a problem with ab screens. After some investigation, it was suggested to increase the centrifuged time to 10 minutes before use.

Dawn Arnett, MT