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James Powell

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  1. Hi Malcolm,

    I was wondering if you could provide some insight on a case I'm writing up for my portfolio,

    It's an antenatal case with history of anti-c (now 4th pregnancy)

    We've referred to RCI each time a sample has come in. The booking bloods identified allo anti-c by "Enzyme IAT" and then quantified (0.2IU/mL). The four subsequent samples identified allo anti-c by "Enzyme Technique" and added that "The anti-c failed to react by IAT and therefore was not quantified"

    I've attended the NHSBT specialist course, but don't recall discussing a non-IAT enzyme technique. Are the reported methods different, and how? 

    1. Malcolm Needs

      Malcolm Needs

      No, between you and me, I think that the reports may have been wrong!

      NHSBT RCI Laboratories used to use red cells treated with papain in a direct agglutination method, but then went over to using red cells treated with papain in an IAT, because we found that we got less "rubbish" reactions, and an increase in sensitivity.  However, the option to use either the term "Enzyme IAT" and "Enzyme Technique" remain on the computer.  It is pedantic of me to say that, in reality, an "Enzyme IAT" is an "Enzyme Technique", and so, in reality, the report isn't exactly incorrect, but I know what you mean; it is confusing.  What confuses me more is, if the anti-c was not detected by a straightforward IAT in the first place (i.e. the red cells were not papain-treated), why an anti-c level was reported in the first place; it should not have been.

      I hope that assuages any dooubts you may have, but, if not, please feel free to get back to me.

      Kindest regards,

      Malcolm

    2. James Powell

      James Powell

      Thank you Malcolm,

      So to clarify, if anti-c is detected by enzyme only quantification is not needed? It is presumably too low for non-enzyme methods? 

      (this was reported by Tooting by the way)

    3. Malcolm Needs

      Malcolm Needs

      Ah, that explains it; I'll tell you why in a minute!

      If either anti-D or anti-c is only detected by an enzyme technique, but not by a straightforward IAT (that is, with untreated red cells), then we should not report the quantification results.  The same applies for other specificities, such as anti-K, anti-Jka, anti-whatever; if we only detect the antibody using enzyme-treated red cells, we should not report a titre, and yes, you are right, an antibody detected by "enzyme-only" techniques has never been implicated in a clinically significant case of HDFN.

      Now then, why did I say "that explains it"?  The answer is that quantification is no longer performed at Tooting, but is performed in Colindale.  The first time a sample comes in during a pregnancy, which contains either an anti-D or an anti-c (or, God forbid, both!), Tooting does the serology, but a sample of the plasma is sent over to Colindale on the same day, and they (usually) perform the quantification on the same day, and enter it into the national computer.  Once this is done, it is almost impossible (not quite, but almost impossible) to take it back off again, and involves paperwork equivalent to an old fashion telephone book for the Quality Department.  After that, however, and as happened in your case, the quantification is not reported (and may not even be performed) unless the antibody has strengthened, and reacts by a "normal" IAT.

      All that having been said, it still is wrong that "Enzyme Technique" has been used, rather than "Enzyme IAT" and, although I am no longer Head of the RCI Laboratory at Tooting (having taken over a national position as Reference Service Manager - Training), I am still based at Tooting, and will go to the Laboratory tomorrow and give them a good kicking!!!!!!!!  All aspects of our reports should always be accurate!

      Best wishes,

      Malcolm

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