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Malcolm Needs

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Posts posted by Malcolm Needs

    Deactivation of Insignificant Cold antibodies

    in Transfusion Services

    Posted · Edited by Malcolm Needs

    Okay, so as long as the said antibody is tested each and every time, to ensure that the antibody specificity has not "broadened", but also that the thermal amplitude has not changed, so that, "this time" it may be a clinically significant "cold-reacting antibody", rather than a clinically insignificant "cold reacting antibody".

    Sadly, it is not even THAT simple (if only), but it depends upon the specificity of the antibody and, to a certain extent, the ethnicity of the patient.  "Cold-reacting" anti-M, for example, is known to be much more clinically significant in people from the Far East (particularly Japan) than in any other ethnic group, as far as I know.

    However, if you take the "antibody" out of the computer system, so that it no longer flags, there is the very real possibility that a formally clinically insignificant "cold-reacting antibody", that has developed into a clinically significant "cold-reacting antibody" may be ignored - not "not detected" (far from it) but ignored, because "it was okay last time"!

    All that having been said, I have NEVER understood why time and money is spent on determining the specificity of a genuine cold-reacting antibody, rather than just determining the thermal amplitude, to determine the clinical significance, and bothering to provide antigen negative blood, when there is zero chance of a haemolytic transfusion reaction!

    ABO for Cord bloods

    in Transfusion Services

    Posted

    The first, and most important, thing to remember is that ABO antigens are "carbohydrate-based" and are not, therefore, direct gene products (not that any antigens are, as every one of them undergo post-translational changes).  The direct gene products are, of course, the A,  B and H transferase enzymes.  At birth, it is incredibly rare for the enzymes to be "working" at its optimum/maximum, so that it is rare for the ABO antigens to be expressed maximally (or anything like) at birth.  I am certain that you know all this already, so that I am probably "teaching my Grandmother to suck eggs", as the old (and in this case, almost certainly, insulting) adage goes.

    As a result of the above, however, unless you can perform A, B and H typing by molecular techniques (NOT to be recommended - see Geoff Daniels book, Human Blood Groups), you either have to decide to ignore all serological cord ABO types, and call all of them O, or, you have to use serological methods that will enhance the antibody/antigen reactions.  Herein, there are inherent problems.

    Firstly, whatever enhancement you use, you MUST use a suitable negative control.  It is fine (in my opinion) to vary the incubation temperature from RT to 4oC, but, to so do, it is very necessary to use another cord blood from a known group O cord sample (i.e. where both parents are KNOWN to be group O themselves, and so an A or B subtype in terms of the control is not a problem).

    Similarly, the same can be said for enzyme-treating the baby's red cells, as long as the control cells are also treated in EXACTLY the same way with the proteolytic enzymes.

    Finally (at least for now!!!!!!!), it should be remembered that we routinely use monoclonal ABO antibodies these days.  These are extremely avid, which is fantastic, but are also VERY specific, which can be a drawback.  By this I mean that the old polyclonal human-derived ABO antibodies we used to use (when I was middle-aged, and Karl Landsteiner was a young boy) had the single (and probably only) advantage that they were not quite so specific, and would, therefore, detect ALL (or most) ABO antigens, including those that the monoclonal antibodies would not necessarily detect.  For an explanation of this, there was a recent paper in Vox Sanguinis (Cripps K, Mullanfiroze K, Hill A, Moss R, Kricke S.  Prevalence of adsorbed A antigen onto donor-derived group O red cells in children following stem cell transplantation: A single-centre evaluation.  Vox Sang 2023; 118: 153-159.  DOI: 10.1111/vox.13386) talking about the A antigen being adsorbed onto the surface of group O red cells in vivo.  One of the references they use is the first peer reviewed paper that I ever wrote, concerning A and/or B substance being adsorbed onto the surface of donor-derived red cells in vivo.  What I failed to say in this paper was that this phenomenon was far easier to detect with polyclonal ABO reagents than monoclonal ABO reagents (36 years, and I still regret this omission!).

    Anyway, IF I HAVEN'T SENT YOU TO SLEEP YET, my point is that, as long as you use suitable controls, particularly NEGATIVE controls, there is no reason why you should not use any modification to any technique (GIVEN THAT IT IS IN YOUR SOP, with all the qualifications given above), and, even then, if you feel it safer, GIVE GROUP O BLOOD.

    Bio-Rad Gel

    in Equipment

    Posted

    The Red Cell Immunohaematology Departments of the National Health Service Blood and Transplant (NHSBT) in England and North Wales have used the Bio-Rad Gel cassettes for years now, and they are absolutely brilliant.  We use them both manually using semi-automated pipettes and reading by eye, and on on fully automated machines with automatic reading.  The ONLY drawback that we ever found was that they are particularly sensitive for detecting unwanted reactions caused by "cold reacting" autoantibodies and cold reacting" alloantibodies, such as sub-clinical anti-M, but I wouldn't swap them for anything.

    Emergency Issue / MTP

    in Transfusion Services

    Posted

    4 hours ago, John C. Staley said:

    When they did sign the form it was most often when the crisis had resolved and the dust settled.

    :coffeecup: 

    I can fully understand what you are saying (and agree almost 100%), but I do have some sympathy for them signing the forms "after the event" as it were, because when they do have to use the uncrossmatched blood that quickly, then they are going to be pretty busy doing things like preventing the demise of the patient - if you see what I mean!!!!!!!!!

    Wrong ABO typing by Gel

    in Transfusion Services

    Posted

    1 hour ago, Arno said:

    The most likely answer has been given above: newly formed autologous red cells have a lower gravity than transfused cells and will concentrate at the top of the re cell pellet whereas transfused cells will seat at the bottom. I hereby attach a paper describing that phenomenon. I hope Grifols will thank you for giving them the answer :-)     20230301142735376.pdf20230301142735376.pdf

    Thanks for this explanation Arno.  I should have thought of it myself (but didn't!) as my friend Bill Chaffe, a former President of the BBTS described just such a situation in a meeting a few years back.

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