Malcolm Needs

Thank you kjmiller. Could be the doctor is being more cautious/more proactive, but in the UK (and I have only ever worked in the UK) our Guidelines suggest/DEMAND that we give K Negative to a patient requiring chronic transfusion, unless they are K Positive (although, interestingly, they are silent on what to give if the patient is K+k-!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!).

The first thing I would ask is, is the lady pre- or post-menopausal? That having been said, in the UK, we tend to give all patients who are likely to be chronically transfused, K Negative blood, whether they be male or female, unless, of course, they are known to be K Positive, purely because the antigen is so immunogenic. As for your question regarding irradiation, that is much more of a clinically decision (I am not, and never have been a Clinician), but I can't see why the units should not be irradiated,

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In that case, I would consider a genotype, as getting hold of M+ N-, S-s-U- fresh units is not going to be easy. That having been said, as you say yourself, anti-N is rarely clinically significant and, if it is not detectable in either the maternal circulation, or in the baby's circulation, I wouldn't worry too much about giving M+, N-, S-s-U- blood. BEAR IN MIND THOUGH, THIS WILL BE A CLINICAL DECISION, AND I AM NOT, AND NEVER HAVE BEEN, MEDICALLY QUALIFIED.

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It is incredibly rare for anti-N to be an alloantibody, unless the individual is M+N-, and also S-s-U-. This is because the amino acids that characterise the N antigen on the Glycophorin A molecule (leucine, serine, threonine, threonine, glutamic acid) are identical to the amino acids that characterise the 'N' antigen on the Glycophorin B molecule. Is the lady of Black ethnicity by any chance? If not, to be N Negative AND 'N' Negative would be almost unique. This suggests to me that the anti-N reported to be in the maternal circulation by the other hospital may well have been an auto-antibody, and would almost certainly be sub-clinical in its significance. In such a case, I would not bother with performing genotyping of the baby's N type. However, as far as Rh, K, etc, I would certainly suggest that antigen negative blood is given to the baby, and I certainly WOULD perform foetal genotyping (see my answer to Cliff above).

The reason I said this (and I admit that I am being more than a little "Reference Laboratory Pedantic here) is because a very good friend of mine (Edmond Lee, who used to work at the NHSBT-North London Centre at Colindale, with such luminaries as Prof Dame Marcela Contreras, Dr Mahes de Silva and Martin Redman, amongst others, who described a case where the bay of a woman with an extremely strong anti-K,, where the baby's foetal K antigens were blocked by the maternal anti-K, and so tested as negative (Lee E, Redman M, Owen I. Blocking of fetal K antigens on RBC by maternal anti-K. Transfus Med 2009; 19(3):139-40. doi: 10.1111/j.1365-3148.2009.00917.x. Later, he reported the same sort of thing with a maternal anti-Fy(a) (Lee E, Cantwell C, Muyibi KO, Modasia R, Rowley M, New H. Blocking phenomenon occurs with murine monoclonal antibodies (anti-Fya) in a neonate with a positive direct antiglobulin test due to maternal anti-Fy(a). Blood Transfus 2015; 13: 672-674. doi: 10.2450/2015.0232-14. Obviously, in both these cases, the maternal antibody was easily detectable, so not the same as the case being described by BullDawgPath, and, in both cases, the baby's DAT was positive, BUT, in both cases, antigen negative blood was required by the baby.

All great questions, but I would also ask, what is the baby's Hb/Hct requiring a transfusion, and why not test the baby's DNA for the gene encoding the antigen cognate to the maternal antibody?

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Um, sorry Jason, but I think you mean Dithiothreitol (DTT), rather than Dichlorodiphenyltrichloroethane (DDT)!!!!!!!

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AGREED - and killing the patient in some circumstances!!!!!!!!!!!!!!!!!!

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Welcome to this AMAZING site Lindsay V. ENJOY!!!!!!!!!

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I agree Darin, it is almost certainly a dilutional effect, BUT, it could also be the effect of a soluble antigen (obviously not within the Duffy Blood Group System). If the antibody had a specificity within, for example, the Lewis Blood Group System, or the Chido/Rodgers Blood Group System, the antigen in the plasma could well adsorb out the circulating antibody. That having been said, this explanation is FAR less likely than your suggestion of the dilutional effect.

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Welcome to this FANTASTIC site CT1988. ENJOY!!!!!!!!!!!!!

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Welcome to this FANTASTIC site Rosanna Cuevas. ENJOY!!!!!!!!!!!