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Malcolm Needs

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Everything posted by Malcolm Needs

  1. Yes, I lived all my life in England, in or around London. The bombs were the Chelsea Barracks bomb in 1981, the Hyde Park Corner bomb in 1982 and the Harrod's bomb in 1983.
  2. Particularly if the massive transfusion event is a major incident, and during a time when there is only a minimum number of people working, we used to have a list of telephone numbers for, primarily, people who work in blood transfusion, but also those who work in blood transfusion as a sort of secondary discipline, and we give this to the microbiologist to contact the required number of staff (on the grounds that the microbiologist, brilliant in their own discipline as they may be, are less likely to be of use in the Blood Bank when units are required urgently, than are the staff who are already running around like headless chickens). I was lucky enough (????????) to be involved with three IRA bombs and two train crashes in my time - and the system did work.
  3. We used to do this with some of our DiaMed cards. It was all to do with micro-bubbles of air that got into the columns during transportation. All I can tell you is that it worked!
  4. But Dad and baby could both be incompatible with mum major side. E.g. Mum could be group A and Dad and baby group B, or have I read this wrong (it wouldn't be the first time)?
  5. The highest percentage of DAT Positive Cord Bloods are as a result of sub-clinical ABO HDFN (say, a group S mother and a group B baby). The next highest in terms of percentage is now D Positive babies of mothers who have been given anti-D immunoglobulin during the pregnancy (most certainly in the UK). Although the DAT is often positive, it is always a sub-clinical condition. Probably the next in line in terms of positive DAT is idiopathic positive DAT in the baby, probably due to non-specific uptake of proteins on to the red cell membrane. Unless the mother has a known atypical alloantibody in her circulation, it is highly unlikely that a positive DAT will result in clinically=significant HDFN (unless the father has passed on a gene to the baby, resulting in the baby expressing a low prevalence antigen on its red cells, and the mother having the cognate antibody in her circulation - but this is REALLY rare). In most cases, do nothing, unless you have time and money to waste. Wait until the paediatrician/obstetrician decides there are clinical reasons to start worrying, rather than just a positive DAT. The baby needs to be treated, NOT the test result.
  6. A fairly short, but very interesting interview with Neil Blumberg in the July 2019 edition of AABB News, as he his one of three new inducts into the National Blood Foundation's Hall of Fame. Congratulations Sir and, from what I know and have read, thoroughly well deserved.
  7. Okay Scott, but can either the clinician, or you, tell me what constitutes a "significant increase"? Surely, the absolute titre is much more significant than an increase? I am not for one moment decrying an increase, that is certainly important, but we also need to know at what titre the anti-S becomes clinically significant in pregnancy. In the original report involving fatal HDFN (Levine P, Ferraro LR, Koch E. Hemolytic disease of the newborn due to anti-S: a case report with a review of 12 anti-S sera cited in the literature. Blood 1952; 7: 1030-1037) the authors state that the titre was between 64 and 128, BUT, it is very important to remember that this was only seven or so years since the IAT was first described, when the sensitivity of the test was, shall we say, primitive, usually involving tile techniques and an AHG made in sheep, goats, rabbits, etc. The evidence is, therefore, not 100% reliable. I would have thought that, in this day and age, it would be much more reliable to monitor any pregnancy by such techniques as ultrasound/MCA Doppler, than by the antibody titre, when we do not know what titre is clinically significant in the first place.
  8. Two reasons. The first is that severe HDFN caused by anti-S is very, very rare, but it does happen. The second, and much more importantly, is that a titre is a snap shot that tells the obstetrician ABSOLUTELY NOTHING in isolation. Supposing the titre is, for example, 512, the pregnancy can be monitored (as it can be anyway, whatever the titre) and there can be clinical intervention, if required. On the other hand, supposing the titre is 2, what does that mean prior to conception? Again, the answer is ABSOLUTELY NOTHING. The baby may not inherit the GYPB*S gene from the father, so the antibody will not increase in titre, or the baby may inherit the GYPB*S gene, but that doesn't mean the titre will automatically rise during the pregnancy, although, of course it can. It sounds to me that the clinicians are fishing, but without either a rod or a net (they haven't got a clue)! I know that the UK Guidelines do not apply in the US, but it might be worthwhile suggesting that they at least read "British Committee for Standards in Haematology (BCSH): White J, Qureshi H, Massey E, Needs M, Byrne G, Daniels G, Allard S. Guidelines for blood grouping and red cell antibody testing in pregnancy. Transfusion Medicine 2016; 26: 246-263 (doi: 10:1111/tme.12299) and/or Royal College of Obstetricians and Gynaecologists (RCOG). The management of women with red cell antibodies during pregnancy. Green-top Guidelines No.65; May 2014. https://www.rcog.org.uk/globalassets/documents/guidelines/rbc_gtg65.pdf.
  9. I'm afraid my answer this time is going to be less helpful, because it very much depends upon the particular technology used by the laboratory, meaning that there is no single answer (and 28 weeks of pregnancy, from this point-of-view, is irrelevant - we would do the same tests at any stage during the pregnancy). The majority of hospital laboratories use a technology known as column agglutination technology, or CAT. With this, the reactants (for example, your plasma and a sample of donor red cells) are pipetted into what is known as a "reaction chamber" at the top of the column, after which the whole thing is incubated at 37oC (body temperature) for about 15 minutes, and the card is then centrifuged at a specific speed for a specific time (there is a bit more to it than that, but I don't want to go into too much detail and confuse the issue). This type of technology is superb for detecting clinically significant antibodies, but can be prone to detect clinically insignificant "cold-reacting" antibodies, that will cause neither a transfusion reaction, nor problems with a pregnancy (haemolytic disease of the foetus and newborn). These are sometimes called "false positives", although, strictly speaking, they are true positives, but not really the type of antibody we want to detect. This is a bit of a nuisance (for us). There are loads of other technologies and techniques, but the Reference Laboratories will have access to almost all of these. In addition, the Reference Laboratories will have access to many more examples of rare red cells and grouping reagents. In a case like yours, I would think that the Reference Laboratory would first work out the actual specificity of your antibody, and then perform tests (probably in good, old-fashioned test tubes) to see whether the antibody reacts at 37oC or at a lower temperature. This will tell them whether or not your antibody will need to be monitored throughout your pregnancy. I would be very surprised, given what you have told us about your case, if the Reference Laboratory would require another sample during your pregnancy, as 28 weeks of pregnancy is thought of as a sort of "cut off" point - BUT, I must reiterate, I am commenting "from afar", for one thing, and, in any case, am not allowed to diagnose or give specific advice to your case.
  10. Thanks ELondon. Could I just say again, even if the Reference Laboratory does detect an antibody (or more than one, come to that), it is not a particularly abnormal thing in pregnancy, but it does not mean for one minute that the pregnancy will be affected; Mother Nature has seen to that. There is another Blood Group System named Lewis. The antigens within this system are soluble in the plasma part of your blood, and are adsorbed onto the red cells from the plasma (they are not intrinsic to the red cell membrane). During pregnancy, the concentration of plasma lipoproteins (fatty proteins in the plasma) can increase enormously (about four-fold). These plasma lipoproteins "mop up" the soluble Lewis antigens, and a pregnant woman, who would normally be, for example, Le(a-b+), can become Le(a-b-), and may even, temporarily, produce antibodies against the Lewis antigens (an individual hardly ever produces antibodies against an antigen that they express - but strange things happen in pregnancy!). In addition, ALL babies are born as Le(a-b-), so any Lewis antigens Mum produces will NOT affect the baby! There are many, many other antibody specificities that will not affect the pregnancy at all. Now, I should say two things. Firstly, I cannot say, from a distance, what is the antibody in your plasma (that can only be done by the laboratories at the Hospital and the Reference Laboratory, but it does not sound at all serious). Secondly, i am what is called a Biomedical Scientist, not a doctor, and so I am, by Law, not allowed to diagnose (as far as I know, neither is the midwife), and this is why I am so glad that you are going to see an Obstetrician, who, I hope, will be able to reassure you even more. Mean while, sleep easier, and enjoy your pregnancy!
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