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Malcolm Needs

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Posts posted by Malcolm Needs

    ·

    Edited by Malcolm Needs
    Brain freeze!

    38 minutes ago, John C. Staley said:

    I'm curious, where does one find rabbit erythrocyte stroma???  Granted, none of my many years were spent working in a dedicated reference lab but I don't remember ever hearing or reading anything about this technique.  :eyepopping:

     

    :coffeecup:

    Rabbit Erythrocyte Stroma (RESt) kits are available commercially, but for the life of me, right at this second I CANNOT remember from which company.  I'll get in touch with some of my colleagues who still work (!) and get back to you.

    I have been reliably informed that the company is Immucor (Product Code 0057316).  I hope this doesn't break any rules about advertising Cliff Reeves.

    Column agglutination technology is an excellent technique, but does have a tendency to detect antibodies that react at temperatures well below 37oC, even after fairly prolonged incubation at 37oC.  However, the fact that the blood group, including the "reverse grouping" is clear of atypical agglutination suggests that this may not necessarily be the case for this patient.

    Just to be on the safe side though, and if you can, I would either treat the plasma from the sample with rabbit erythrocyte stroma (which will adsorb out most "cold" agglutinins), treat the plasma with 0.01M dithiothreitol (which will denature the J-chains of IgM molecules, meaning that, although they can still sensitise the red cells, they are no longer able to agglutinate the red cells) or, and my personal favourite, is to pre-warm the plasma and red cells to 37oC before mixing, perform the IAT at strictly 37oC in glass tubes, wash with saline warmed to 37oC and use monospecific AHG.  If any, or all, of these techniques lead to negative results, the chances are that the antibody is a clinically insignificant "cold" IgM antibody, such as an auto-anti-HI (given that the patient is group A, and the test cells are all group O)..

    Failing the above, send a sample to a red cell reference laboratory.

    I hope that helps a little bit.

    ·

    Edited by Malcolm Needs
    Spelling (as ever!).

    Many, many years ago now, when I was working at the old Westminster Hospital in London as a quite junior member of the Blood Transfusion staff, I spent quite a few hours working on a sample from a patient with a positive DAT, trying to determine the specificity, in order to see whether the antibody was an allo- or an auto-antibody.  This included the use of several very rare red cells that I had frozen down and also examining the eluate.  After many happy hours, I had got precisely nowhere, and so sent a sample to my former colleges at the International Blood Group Reference Laboratory.

    I received a somewhat "spicy" report from my heroine Joyce Poole, who explained to me, in words of one syllable, that I had rather been wasting my time, rare cell collection and the laboratory's money as, in almost all cases, the specificity would be found to be an auto-anti-Rh17 or auto-anti-Rh18!!!!!

    Since then, I have reverted to doing as little as possible on such samples and, when I retired 43 years later, and, as far as I know, none of the patients ever died as a result.  There was a close one once, when I was working on a sample on a Saturday on-call in the Red Cell Reference Laboratory at NHSBT-Tooting Centre.  I was working on a sample that was overtly a case of wAIHA.  After several allo-adsorptions, I was finally able to provide "suitable blood".  It was only at the last minute that the computers came back on after an unplanned downtime, and it appeared that the patient was known, from many years previously as having an allo-anti-Vel!!!!!!!  As you can imagine, I did several more tests before I released the blood (on Pathologist's orders), as there was absolutely no evidence of an anti-Vel (auto- or allo-) in the present sample - but it did give me a bit of a turn!!!!!!!!!!!!

    I would recommend a thorough reading of Petz LD, Garratty G.  Immune Hemolytic Anemias.  2nd edition, 2004, Churchill-Livingstone. ISBN  978-0-443-08559-8.

    Other than that and, possibly, looking at the patient's sample at a more molecular level (as noelrbrown suggests above), I really wouldn't do much else, except that I would put a little note with the blood to be transfused to remind the doctors and nurses on the ward to be vigilant with their patient observations.

    ALL OF THE ABOVE HAVING BEEN SAID, I AM NOT, AND NEVER HAVE BEEN, MEDICALLY QUALIFIED!!!!!!

    If it is reacting with al cells other than the patient's own red cells, then the chances are that it is an antibody directed against a high prevalence antigen, BUT, it could be a mixture of more than one (more common) specificity or, worse, a mixture of an antibody directed against a high prevalence antigen (e.g. an anti-Vel) and against a polymorphic antigen (e.g. an anti-Jka).

    This is why I say it is important to actually have the specificity/specificities sorted out as soon as possible, because the foetus/newborn may need a transfusion, and/or the mother may need a transfusion (possibly both, and possibly in a hurry).  There may be very little time towards the end of the pregnancy.

    The antibody may well have a specificity that is not clinically significant to either the foetus/newborn or the mother, but it is best to know.

    It is most unlikely to be anti-f, as this specificity will not react with either R1R1 or R2R2 red cells (I presume that you are using both antibody screening cells and antibody identification panel cells that have these phenotypes represented).

    Anti-f reacts with red cells where the c and e antigens are the result of an RHCE*ce haplotype where, for want of a better way of putting it, the c and e antigens are the result of the RHc and RHe genes being in the cis position - NOTE THAT THIS TERMINOLOGY IS (KNOWINGLY) WRONG!

    Like all Rh antibodies, anti-f reacts most strongly with its cognate antigen on red cells that have been treated with a proteolytic enzyme (such as papain or ficin), but will very often react with untreated red cells by IAT.

    My immediate thought is that they should have sent the sample on to Red Cell Reference at the IBGRL.

    If they have also detected an antibody by IAT and enzyme techniques, that is not reacting with autologous red cells, and, as the DAT is negative, the specificity needs to be sorted out as early as possible in the pregnancy, in case the antibody is 1) clinically significant and 2) becomes more potent during the pregnancy.

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