Malcolm Needs

Thanks for your comment pluto, which is much appreciated, but to be fair to eric 1980, I'm not sure that he is saying he actually takes the serum/plasma off the red cells, but only separates them by centrifugation; in other words, ensures that the serum/plasma is free of white cells and/or platelets prior to testing, but I am prepared to be rebutted.

Hi David, I am intrigued! If the person sends you the message again, would you consider posting it (with, of course, permission from the sender)?

Hi eric 1980, I agree with everything Rashmi says. It may well be that your modification of centrifuge speed and time is fine, but if you were working for me, and I found that you were altering the speed and time of centrifugation during the night shift without a) performing a fully documented Change Control and getting my permission (as Manager) you would be in grave danger of meeting with Human resources so fast that your feet wouldn't touch the floor. If you are a scientist, you have got to be prepared to prove that any changes you wish to make will be at least as good, or better than what you want to change. If you are not prepared to do this before you choose to use your change on live patient samples, then you would thoroughly deserve the meeting with HR. :mad:

Okay, I understand that GilTphoto, but when the feto-maternal ABO is compatible, and the mother is not known to have any atypical alloantibodies directed against the major blood group antigens, how many positive DAT's do you actually see that are, a) due to an antibody in the mother that is directed against a low incidence antigen expressed on the baby's red cells, and how many of these result in clinical, as apposed to sub-clinical HDN? I suspect it is disappearingly few. It is rather the same situation as that with the differentiation between delayed haemolytic transfusion reactions and delayed serological transfusion reactions; the latter being commonly detected in the laboratory, but being of no clinical significance whatsoever.

Hi Mau Feitio, I have sympathy. This is such a waste of time, money and resources. What could a DAT possibly add to any diagnosis in this situation. If the mother has an antibody, great, do a DAT, but if that is positive, it means absolutely nothing, unless the baby's Hb is low or the bilirubin is high. In other words, it is a confirmatory test. If there is no known atypical alloantibody, what on earth is the point of doing a DAT unless and until the bay is showing early signs of HDN. I think that it is a combination of ignorance on the part of the Obstetric team (because they now have to know so many other things in detail that they no longer learn the basics) and the fear of being sued if they forget a particular test, so they order every test under the sun.

Hi Rashmi, In the NBS (NHSBT) we use something called QPulse5. It is excellent, but I would not be the correct person to explain it. Perhaps if you give a call to the Quality Department at Tooting, they would be able to give you more, and more useful information.

Hi dawntr50, In Hot Topics you will find a thread named Antibody Identification Algorithm. This was aimed at your post, but I could not for the life of me remember where I had seen your post (I've now, obviously, found it). The algorithm may be of absolutely no use to you whatsoever, but it's there if you haven't seen it.

Actually, transfusionpgi, I wouldn't be at all worried that you found an anti-Mia in your population. It's not the frequency of the antibody that matters, but reather the frequency of the antigen in the population. We recently had an Lu:14 in one of our panels (I know not why) and, as a consequence we found a couple of anti-Lu14s, but they didn't matter because Lu14 is so rare. Also, you will find that, very often, once an individual has made an antibody against one low frequency antigen, they very often make a whole soup of antibodies against other low frequency antigens. You also have to be mighty careful that the red cells you are using that are "typed" as, for example, Wr(a+) are really Wr(a+). In other words, they have been typed using a reputable monospecific anti-Wra (or genotyped) and not with an antiserum labelled as anti-Wra, but which itself may have many other antibodies in it directed against low incidence antigens. It is an area fraught with danger for the unwary!

I'm just wondering if he had a mixed-typed cold and warm auto-immune developing. They are very rare (well, quite rare) but they do exist. Did you try warm-washing the red cells prior to re-running the tests?

You'll have plenty of time between your re-validations of your automation! SORRY!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I agree with all you are saying, but even then, I cannot see it adding up to a 20% discrepancy.

This seems an excellent method of identification - and a good deal less expensive than my suggestion of RFID!

I must admit, I am struggling to think of any antigens found on the Indian sub-continent that would cause such a high frequency of false negative reactions. Even within this population, the In(a) antigen is not that common. I know that in the Peoples' Republic of China they have to include red cells expressing Mi(a) and Di(a) because of the relatively high frequency of both these antibodies and antigens in their population, but I still can't think of such a combination in India. I worry that it is the technique being used, or that cells expressing single dose of antigens (e.g. S+s+, Fy(a+b+), Jk(a+b+) are being used in the screen - screening cells should always express single dose) or that the red cells are not kept in a preservative/stored at a sub-optimal temperature (or a combination) but other than that I am stumped.

In the case of most, if not all, monoclonal IgM grouping reagents, you should be able to use your normal controls, unless the auto-antibody reacts at the same temperature as that recommended for the incubation of the grouping reagents. In the case of IgG antibodies, whether monoclonal or polyclonal, the chances are that you will not get true negative reactions (unless of course, the DAT is caused by a "cold-reacting" antibody of narrow thermal range, and only involves a C3d or IgM and C3d coating, and as long as the incubation is at 37oC). You could try coating some red cells with a known IgG antibody to use as positive/negative controls. Lastly, you could try treating the patient's red cells with dithiothreitol (DTT) or ZZAP, but have a care, as some antigens are sensitive to this and are destroyed. It is worth looking in The Blood Group ANtigen FactsBook by Marion Reid and Christine Lomas-Francis, 2nd edition, Elsevier Academic Press, 2004 (ISBN: 0-12-586585-6, Library of Congress Catalog Number 2003102995) for a list of such antigens - it's a fabulous book! I'm sure other people will have other ideas, but I hope this is of some help.

Hi R1R1, Having recommended Jeff McCullough's book, here is another book that makes really interesting reading on the subject, and goes into the history of why and how the US Blood Services have evolved. It is BLOOD An Epic History of Medicine and Commerce by Douglas Starr, Little, Brown and Company 1999 (ISBN: 0-316-91146-1). I'm afaid that I do have to say that it is a little "US-centric" (individuals such as Robin Coombs, Rob Race and Patrick Mollison hardly get a mention) but that does not take away from the interest.

Mary, you are an absolute star! Thank you!

I'm sorry I'm causing you so much trouble Mary. If you really don't mind, the address is: Mr.M.E.Needs CSci FIBMS Reference Service Manager Red Cell Immunohaematology Department NHSBT-Tooting Centre, 75, Cranmer Terrace, Tooting, SW17 0RB England If I am causing you too much hassle, don't worry about sending it.

Hi Mary, That is really kind of you. I have a fax number at work. The number is 0208 258 8350. Of course, it's in England, so I think that you have to put 44 in front (but I'm not sure)!

Hi Mary, Is there any chance you could scan it and send it to my home email address? malcolm.needs@blueyonder.co.uk

Hi yolis76, I have a PowerPoint lecture and accompanying Word Document that may help with your understanding of antibody quantitation. It's only 13 slides long, but I can't seem to upload it via the website. I would be happy to send it to you if you supply me with your email address (either your own or your work). If you would like to send it privately, my own email address is malcolm.needs@blueyonder.co.uk.

Hi eeagan, I can understand this for routine samples, but what happens if you have real emergency? Presumably you issue group O RhD Negative cellular products and, possibly, group AB plasma products? I'm thinking of an exsanguinating patient in Accident and Emergency.

LShirley makes a good point. By the way, what was the patient's diagnosis? I suppose that they hadn't been given ALG or something similar? Again, only speculation on my part.

I couldn't agree more with you LShirley, but David is absolutely correct about loading the chamber properly. Unless you know for a fact that the individual has been transfused, it's always worthwhile repeating the test.

I agree with David, except that we do see mixed-field reactions with A3, even though all of the red cells are really group A. We once picked up a true chimera by ABO too. You can't get much more of a genuine mixed-field than a chimera!

I agree wholeheartedly with you. Come on out there!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!