Malcolm Needs

It doesn't bother me in the least John - but it might get others talking!!!!!!!!!!!!!!!!!!!!!!!!!

You are completely correct Lecia; serological cross-matching WILL NOT detect all incompatible units. There are many clinically significant atypical alloantibodies in patients (particularly Kidd antibodies) that will only react with homozygous expression of their corresponding antigen. This is why screening cells and antibody panel cells are chosen to have homozygous expression of certain antigens (and in some cases are actually checked by genotyping or flow cytometery) and are in preservative. As I wrote in another post, this preservative is designed to preserve the antigenicity of the red cells, but not the oxygen carrying capacity. On the other hand, units of blood are in a preservative designed to preserve the oxygen carrying capacity, but not the antigenicity. Therefore, if you have, for example, a weak example of anti-Jka, that only reacts with red cells showing apparent homozygous expression (Jk(a+b-), and you cross-match an "elderly" unit of mis-labelled Jk(a+b+) blood serologically, it will not necessarily be incompatible. Scares me to death sometimes! :eek::eek:

Hi, The units are tested by automation from start to finish and the results MUST be downloaded automatically with no human intervention. Any groups that the automation does not recognise without human intervention means that the unit is discarded. All units are typed twice for ABO and RhD irrespective of the number of times the donor has given. All labels giving the groups are produced automatically and contain the unit's bar code, which is matched with the bar code on the unit before it is attached to the unit, and again afterwards. All the bar codes are scanned to ensure that they are all the same prior to the units leaving the Blood Centre.

These sorts of automated expressors (I'm not sure of the actual type) are used universally within the NHSBT.

Slim to anorexic!

Agreed, but also beware of ignoring weak reactions with the anti-e, without a thorough investigation, particularly if the patient is from the Black population; it may be a case of CdeS.

I agree that typing may have been incorrect, but unless this is the case (or the donor has had a stem cell transplant), I cannot think of a situation where a donor may gain an antigen (unless you are counting something like T activation). We (that is, the NHSBT - I am not involved personally) have been looking for the exposure of neo-antigens in blood that has passed through a prion filter and, as far as I am aware, none has been found. I can certainly cite quite a few cases where an antigen has been weakened, even to the extent that an apparent alloantibody may be made against the antigen, but, except in the case of a Lewis antigen, such a situation only occurs, as far as I am aware, in a pathological condition. I have never heard of this happening in a healthy individual. Were it found that a healthy donor has "lost" an antigen, however, I cannot see how it is likely to be clinically significant for the recipient of that blood. The NHSBT now garuarantees that the blood in a unit is of the ABO and D type advertised on the label (the same applies to other antigens printed on the label). In the case of a new donor, each antigen is tested twice under positive sample identification, and each antigen on the label is tested at least once on that actual donation on any regular donor. As a result, very few of the hospitals we supply with blood now actually test the group of the unit.

Right then Kate, I've finished doing my ferreting around, and here is the answer. From the BCSH draft irradiation guidelines 2009: "TA-GVHD has not been described following transfusion of frozen deglycerolized cells, which are in any case thoroughly washed free of leucocytes after thawing." Recommendation. For at-risk patients, all red cell, platelet and granulocyte transfusions should be irradiated, except cryopreserved red cells after deglycerolization. It is not necessary to irradiate fresh frozen plasma, cryoprecipitate or fractionated plasma products." So it would appear that, more by luck than judgement, I was correct! :):)

In a way, you are asking an impossible question, as It depends upon the size of the individual and, therefore, their blood volume. It also depends upon how much colloid/crystalloid has been transfused to maintain this blood volume, and in the case of a colloid in particular, the average molecular weight of the preparation, as the lower the molecular weight the quicker the colloid is cleared from the circulation (but the faster liquid is drawn into the circulation from the interstitial spaces) and vice versa. I would, therefore, thoroughly recommend reading Chapter 2 of Mollison's Blood Transfusion in Clinical Medicine, Harvey G. Klein and David J. Anstee, Blackwell Publication, 11th Edition. This is not, in my opinion, an easy read (although, again, in my opinion, it is easier to read than some of the earlier editions!), but it does give all sorts of mathematical equations to help estimate blood loss and how much is required to bring the patient back to some kind of normality. I am certain that other posters will be able to answer your question better than I, but it's a start. :)

Once again, I'm not sure and will find out, but, certainly, red cells from sickle cell disease patients do not freeze, thaw and reconsitute very well (however, rare their blood group may be)!

Just to confirm what you say, Malcolm - I've seen 2 cases of C-Cw+ over the last 5 years

Thanks for that.

I'll be honest with you, I don't know the answer (but I am going to find out from the National Frozen Blood Bank early next week). That having been said, I would not have thought that there were sufficient viable T lymphocytes to cause GvHD in frozen red cells. As I understand it, the red cells are thoroughly washed before addition of the freezing mixture, and then thoroughly washed again whe they are thawed and reconstituted. Therefore, I would have thought that irradiation after cryopreservation was a step too far (whether I am right or not we will find out next week, and, even if I am, whether the FDA would agree is another matter). This is a very different process to the cryopreservation of stem cells when, of course, the white cells are deliberately kept viable. We have a couple of cancer hospitals in our area, Anna, that will only accept irradiated blood and cellular blood components, just in case there are viable T lymphocytes present and these are transfused to immunocompromised patients; and this is despite universal leukodepletion this side of the pond. It's a pain, to be frank!

How long ago was this? The reason I ask is because the seperation of plasma from red cells is much better controlled now than back in the days of yore, when quite a substancial amount of red cells could creep into the FFP.

Hi David, We've currently got a patient with exactly the same phenomenon from one of our hospitals on the south-east coast of England, even down to the same specificity. Once again, I know for a fact that this patient has not received any K+ blood now for years, has been tested to death to make sure they are not a K+ themselves (possible not the best way I could have put that I think) and yet we consistently can elute anti-K from his red cells. I was (and am ) as confused as you, but I spoke to Joyce Poole (Manager of Red Cell Reference at the International Blood Group Reference Laboratory) about the case, and she thinks that it may be a mimicking auto-antibody, rather in the same way that, very often, an apparent auto-anti-e or auto-anti-E are not actually specific for the corresponding antigen, but react preferentially with these antigens. In other words, she is suggesting that our patient (at least) has made an apparent, but not actual, anti-K that is, in fact, an auto-anti-K-like antibody. I'm not sure if this is the correct answer, but I am certainly NOT going to argue with Joyce!!!!!!!! :)

We do almost all of our antigen testing via DiaMed gel cards, have done so for a good five to ten years now and have experienced no problems whatsoever. Obviously, you have to validate each of your antisera before use, and then validate each new batch, but as you would be running positive and negative controls with each batch of tests you are performing, this is not as onerous as it sounds. We use the same method as swede. :)

Totally agree Rashmi.

I agree that it would Mary, but there are ways around it that, perhaps, should be added to the standard SOP. I presume, by FMH screening, you are using an anti-D to see mixed-field/rosetting? If you are getting such strong results (and these are true results) it is a fair bet that the baby would be anaemic. It might be worthwhile writing a step into the SOP saying that the baby's Hb should be estimated. If this is normal, or near normal, it may be a guide that other tests need to be performed. In such a case, a KB would, of course help, but if this is also positive (because there has actually been a slight FMH, or because the mother has elevated HbF), then testing by FITC conjugated anti-D with flow cytometery may help. This would give an enormously positive result (if the mum is a weak D [and, in many cases, but not all of course, if the mum is a partial D]). This result will be at odds with the slightly positive KB result if there has been a slight (or no) FMH (although it will not help in the case of the mother having a high HbF level). In this case (the high maternal HbF) using a conjugated anti-HbF may help (but this method has not, as far as I know, been fully validated anywhere). Having re-read this post, I not sure that it will help, or muddy the waters even further (but it is an attempt to help)! :confused:

Couldn't agree more with you. :D:D:D:D

True, very true.

This is, by no means, my area of expertise, but I can quite see from where Mary is coming.

I don't wish to be more controversial than normal, but I just wonder if this thread should have been started after the current NEQAS exercise had run its course, rather than before? The reason I am saying this is that (fairly obviously) both NEQAS and the manufacturer of the analyser have got to hear that there is something amiss with one of the NEQAS samples containing an anti-K. NEQAS are upset that telephone calls have been made between sites asking what the others have got, before the exercise has been completed. It has to be remembered also that there are very many UK members of BBT, even if not too many of them post on a regular basis. Over this, I think I can see their point. Such telephone calls immediately alert people to the fact that there may be a problem. As you say, Rashmi, this may be a "difficult area" for certain people. If they did not know that there was such a problem, they would have put in "negative" results automatically for the screen, because that is what they have found. Now that they have been alerted, however, they are going to "test to competency" (I think that is the phrase you quoted in another thread about the MHRA), and NEQAS will then get "false" answers. This may, on another occasion/exercise mean that a problem is not flagged up by a trend. Sorry. I know I sound a bit grumpy over this one, but I can see from where NEQAS are coming. :confused::confused: Because not everyone is as honest as you, therefore, if there is a real problem with one make of analyser, the seriousness of the problem will be "diluted" by the fact that some people may test the exercise plasma to destruction, until they get the desired (or "broadcast") answer, and put in the fact that they detected the anti-K, even though, in reality, they did not, until they were made aware that there was this anti-K present.

They're Gods aren't they!!!!!!!!!!!!!!!!! :sarcasm:

The other thing is to be absolutely sure that your enzymes are pure. Trypsin is very often contaminated with a small amount of chymotrypsin, which will ruin your tests.

I have never seen it myself, but have read about it in the earlier editions of Mollison. Apparently, there can be red cell membranes in the FFP that have intact RhD antigens. They are insufficient in number to cause primary response, but can be in sufficient numbers to cause a secondary response. If your patient had already been sensitised to the RhD antigen, either by pregnancy or by a previous transfusion (even many years ago), the anti-D may well have become serologically undetectable in the screen, but the memory cells in her circulation would still be sensitive to a second (or subsequent) immunological challenge by the RhD antigen. By no means am I saying that this is the case with your patient, but it may be the answer. :confused: