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Ortho Notification 7 Oct 2015

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Hi everyone,

I just received a notification from Ortho about recently transfused patients and interpretation guide.

 

"Following centrifugation of a freshly collected patient sample drawn from a recently transfused patient, the potential exists for the donor's transfused red cells, which are denser and heavier, to concentrate at the bottom of the sample tube in a layer below the patient's own red cells, which are less dense and lighter.  If the cell suspension used for testing contains a majority of transfused donor cells, unexpected patient results could be observed due to the patient cells being an absent or minor population in the prepared cell suspension.  The unexpected patient result could be a result associated with the transfused donor cells, or it could be due to a mix of patient and donor cell populations"

 

 

Currently I use gel for antibody screening and id and gel crossmatches only...no antigen typing or ABO typing. 

 

 

Do you think that I would have to change anything in my SOP's?

 

Thank you.

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This is not new, and it is not specific to Ortho or gel.  It all depends on where you take the cells from in the original sample.  You can get a different result if you take from the bottom or take from the top.  In general, automats take from the bottom; whereas if you work manually you take from the top.  So you can get discrepant results.  And before everyone starts panicking, this does NOT happen very often.

All the more reason to review your results carefully and with a good dose of common sense!

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Yes, as Anna says, this is not anything we haven't known already. An antigen phenotype is not accurate if the patient has been transfused in the last 3 months. Very easy for us to see on our automated method; the results are mixed field.

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Thank you everyone - I know that antigen typing is not accurate on recently transfused patients, and have addressed that in other SOP's.  This notification was specific to gel testing. 

 

Now that galvania explains it that manual processes take the sample from the top, and automated instruments sample from the bottom of the cells it all makes more sense to me.

 

Thank you again.

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OK once again it's time to show my ignorance for being away from blood bank as long as I have but, I don't recall ever hearing that donor cells are denser and heavier.  We did not put any faith in antigen typing anyone who had been transfused in the previous 3 months but for some reason this is new info for me.  Can anyone tell me why the donor cells are denser and heavier?  Is it storage, or the anticoagulant?    :confuse:

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According to the Ortho document, the donor cells, as they age, become a more homogeneous population of newer red cells, whereas a normal human being has an equal distribution of day 0 and day 120 red cells.  According to them, the older cells are lighter and the newer cells are heavier (for example reticulocytes are larger).  So the older cells in the bag of donor blood die off, leaving the newer population of heavier cells.

 

So the bag is not uniformly mixed...but then the whole story gets muddy when you think about the recipient incorporating those donor cells into his/her circulation.  From what I recall, those donor cells are cleared out at a faster rate than patient's own cells, so I find it a bit implausible to find a layer of heavier cells sitting at the bottom of the packed cells but that is what they are saying at Ortho.

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It's important to realise that this does not happen EVERY time.  It depends on a number of variables, including whether the patient was anaemic in the first place, and how much blood is transfused, how much the patient is bleeding etc etc..  And I've seen it several times.  Different results depending on where you take your sample from.  I must have some literature on this - MUCH older than Ortho's notification - as I said before, this really is not new - I'll see if I can dig it out.  And incidentally, this is the principle on which you can separate transfused and 'own' cells . And I repeat - this is nothing to do with gel.  Test in tubes and, for samples that are affected, you can see the same thing depending on where you take the blood from in the sample tube.

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According to the Ortho document, the donor cells, as they age, become a more homogeneous population of newer red cells, whereas a normal human being has an equal distribution of day 0 and day 120 red cells.  According to them, the older cells are lighter and the newer cells are heavier (for example reticulocytes are larger).  So the older cells in the bag of donor blood die off, leaving the newer population of heavier cells.

 

So the bag is not uniformly mixed...but then the whole story gets muddy when you think about the recipient incorporating those donor cells into his/her circulation.  From what I recall, those donor cells are cleared out at a faster rate than patient's own cells, so I find it a bit implausible to find a layer of heavier cells sitting at the bottom of the packed cells but that is what they are saying at Ortho.

 I believe you have this backwards.  The patient cells, which are more likely to contain reticulocytes, will be lighter and at the top, with the older donor cells towards the bottom. That's providing the patient is not aplastic and is actually producing RBCs. This is the premise behind the reticulocyte separation method which has been used as a method to attempt to phenotype a patient that has been transfused.

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This was the theoretical basis for reticulocyte harvesting with microhematocrit tubes when you wanted to phenotype a recently transfused patient. 

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SMW - thank you for the info about reticulocytes being lighter - I would have imagined them to be heavier since they are larger, but I believe you! 

 

I stand corrected! :)

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Column agglutination technology (Gel) does a superior job of detecting mixed populations of red cells in a blood sample compared to standard tube technology.  Having done ABO/Rh typing on ProVue since 2004, I've seen dozens of samples with dual population due to transfusion of a single unit of RBC that was not ABO/Rh identical to the recipient.  I think these mixed-field reactions (typically be missed in tube) are clearly visible in Gel.

 

Using an unspun sample of blood to do a forward ABO grouping isn't wrong, but is it really necessary to do this routinely on all blood samples?  Does the SOP give any explanation for this approach?

Edited by Dansket

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I don't see any wording explaining it.  

I'm accustomed to mostly gel and the Provue.

 

Here they do a forward and reverse in tubes but a manual gel antibody screen.  I'm not sure if I'll ever get them to go full gel.

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So you do the forward group using whole blood; then you spin the sample to do your reverse and antibody screen?.  Well, nothing wrong with it but it sounds like a very roundabout way of doing things!

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yep!  Id say they are still a little old fashion.   I was shocked when they said they were doing Electronic XM's.

 

They way they have explained it to me is that they like to have a forward and reverse done very quickly for emergencies.  We only keep 10 O neg units on the shelf and we are 70+ miles away from our blood supplier.  In the state of emergency after they have a forward and reverse done they will emergency release type specific blood. This is how our pathologists like it to be.

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amym1586,

 

How often do these emergencies occur?  Why do they treat every blood sample as if it is a potential emergency? 

When did the last emergency occur and how many units of ABO identical blood were given based only on a forward typing.

How many minutes do they centrifuge these blood samples?

 

Dansket

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Looks like that last time we emergency released blood was July 2015.  And the last emergency that used type specific blood was March 2015.  I'm new to the lab and even newer to this blood bank sup position.  If I stay here long enough I'll probably try and make some changes for now I just want to make sure we are doing everything correctly!

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I think the concern here is not regarding gel testing but may be referring to the fact that (as far as I know) all automated analyzers sample their RBCs from the bottom of the specimen tube (for the simple reason that the instrument does not detect where the cell/plasma interface is). Therefore, if the population of RBCs at the bottom of the tube might be skewed toward transfused cells such testing may be erroneous. 

 

However, since we do backtypes, unless we have totally diluted out the patient's antibodies we will always be able to catch a discrepancy and resolve it manually.

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