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Brenda Hutson

Questionable blood types

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Our new supervisor wanted me to see what others are doing with regard to questionable, weak blood types. Specifically, if for example the forward type is strong but the reverse is weak (say <2+) and there was no obvious explanation for the weak reverse type (immunodeficiency; elderly; etc.), would you still call out the blood type, or would you call it inconclusive based on not having an explanation for the weak reverse type?

i.e. Anti-A=4+  Anti-B=0  A1C=0   BC=W+

Without an "obvious" explanation for the weak reverse, would you report the patient as group A or would you report it as inconclusive and transfuse group O RBCs?

Thanks in advance for replies,

Brenda Hutson, MT(ASCP)SBB

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I would do a bit more work on it.

There are two things I would do.  Firstly, I would incubate a 4oC (but would include a group O cell in the reverse in case there is a "cold" auto- or allo-antibody there).  Secondly, I would papain or ficin treat the reverse red cells (including a group O cell again as a negative control).

As long as the group A and group O red cells remain negative, and the B cells react more strongly, but not as strongly as normal, I would be happy to call it a group A.

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I would add more antisera and/ or incubate the forward test at 4 degree C to see if there are B antigens here, if negative then  adsorption and elution on the forward B antigens to see if it is existed. The most important thing as Malcolm mentioned above keep a group O cell as negative control.

If all the above tests are all neg, then I will call it A type with weaken anti-B.

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Our site would do the same as Malcolm suggested. We would enter an internal note on the patient record about the weak reaction so techs would be aware when any future workups were ordered.

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Thanks for your replies.:)  Yes, I know about the various "complex" ways to determine true blood type, but we are a small rural hospital so enzymes and absorption/elutions are out. :P I really just wondered how comfortable folks were with calling out a type when:

a)  You have done all of the basic tests (i.e. incubation; extra plasma; etc) and it still comes up weakly positive.....and

b)  There is NO obvious explanation (i.e. age; diagnosis; etc.) for the weak reverse type.

I have worked in several places that won't call out the type unless it is at least 2+ (unless they can explain why it is that weak).......but just wondering what other folks out there are doing.

I very much appreciate all input!:D

Brenda Hutson, MT (ASCP)SBB

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Well if this is a patient, the worst case scenario is that the patient is actually an AB with an atypical weak B antigen that is not being detected and a weak anti-B in his plasma.  So what would happen if you gave group A blood - nothing.  If it's a donor, then you surely have the possibility to do extra work ups - but you would be unlikely to cause any harm if you called the donor a group A.  And there are SO many reasons for having weak ABO antibodies - not least because we have the tendency to be too clean around our kids!

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If the forward type were at all weak, I would worry more about a false positive there which would be a problem but with a 4+ the forward type is more accurate.  What we often do is call the patient A pos (this keeps the computer happier for one thing) but give O blood (put a note/special need in the computer to give O blood for now).  Once we type this patient several different times this way, we might be willing to give A blood.  If it's not going to deplet the O blood supply, we might stay with O.

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Thanks Mabel.  That is what I am wondering....how many places have a policy of giving Group O to patients when typing results are not as strong as one is used to seeing (and the group A example I gave is just one possible scenario of unexpected weak reactions.....and as 1 person pointed out, it could be the forward type also).  So when do you go out on that limb and go ahead and call the blood type with weaker than expected reactions......vs. when do you take the conservative stance and give group O RBCs?  And perhaps for some of you, it is a combination of the 2.....you maybe interpret them as group A but conservatively transfuse them with group O RBCs (as Mabel pointed out.....and I know there are more of you out there because we did that in some places I worked at)?? Inquiring Minds want to know.

I REALLY appreciate everyone's input. :) 

Brenda

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There is no doubt that today's monoclonal antibodies are far superior to the old polyclonal human-derived antibodies we used to use, but, beware of relying too much on their specificity.  Admittedly the following is to do with monoclonal anti-D reagents, rather than ABO reagents, but remember this.

Thorpe et al1, 2 have reported that monoclonal anti-D molecules possess a V4-34 moiety, that is also present in anti-I and  anti-i.  As a result, if papain-treated D- red cells are tested with such antisera, or untreated D- red cells are tested with such antisera that have not been brought to room temperature, they may agglutinate.  This could result in D- red cells being mistyped as D+ - a particular danger in females of child-bearing potential.

1.  Thorpe SJ, Boult CE, Stevenson FK, Scott ML, Sutherland J, Spellerberg MB, Natvig JB, Thompson KM.  Cold agglutinin activity is common among human monoclonal IgM Rh system antibodies using the V4-34 heavy chain variable gene segment.  Transfusion 1997; 37: 1111-1116.

2.  Thorpe SJ, Ball C, Fox B, Thompson KM, Thorpe R, Bristow A.  Anti-D and anti-i activities are inseparable in V4-34-encoded monoclonal  anti-D: the same framework 1 residues are required for both activities.  Transfusion 2008; 48: 930-940.

Of course, in the "old days" of monoclonal antibodies, some anti-B reagents would detect Acquired-B, so monoclonal antibodies cannot be entirely trusted.

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Yes, that's true, Malcolm.  On the other hand, if you test with 2 different monoclonal anti-A reagents (and an anti-AB for good measure - a real one not an A+B) and they all come up 4+, I think it's fairly safe to say that the patient is a group A.  I think that giving group O blood in this case is both wasteful of group O blood (unless you are swimming in it) and overkill

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2 hours ago, galvania said:

Yes, that's true, Malcolm.  On the other hand, if you test with 2 different monoclonal anti-A reagents (and an anti-AB for good measure - a real one not an A+B) and they all come up 4+, I think it's fairly safe to say that the patient is a group A.  I think that giving group O blood in this case is both wasteful of group O blood (unless you are swimming in it) and overkill

Agree 100% Anna!

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On 11/19/2018 at 8:31 PM, galvania said:

Yes, that's true, Malcolm.  On the other hand, if you test with 2 different monoclonal anti-A reagents (and an anti-AB for good measure - a real one not an A+B) and they all come up 4+, I think it's fairly safe to say that the patient is a group A.  I think that giving group O blood in this case is both wasteful of group O blood (unless you are swimming in it) and overkill

I agree with you if transfusing RBCs, on the other hand, plasma transfusion, I think it is safe to test if the weak B antigens exist or not.

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14 hours ago, Mabel Adams said:

What we do might depend on if I am here and see the reactions or if I am handling it by phone at 2 AM.  I have had calls where what I heard them ask was not what I found when I got to work the next day.

I can relate to that! I can log in to my work desktop from home, so sometimes I ask them to fax a copy of what they are doing to my work email (secure!) and I can see what they've documented. Once we're up with our new blood bank system, I'll be able to access that as well. That can be an enormous help sometimes with the ones who don't communicate well.

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I would check your package insert for the reverse cells.  If it states something like this "The ABO antibodies of most group A, B or O adults agglutinates A1, A2 and B cells strongly (3-4+). Reactions of 2+ or less may indicate the reaction is due to an antibody other than anti-A or anti-B. Thus, weakly positive reactions should be evaluated carefully to ensure no ABO discrepancy exists and the correct ABO group is assigned.", then I think you need to do more work at least initially.   Maybe not every time you see the patient, if your medical director is ok with having a know weak backtype not being worked up.

We start with a 5-15 minute room temp incubation, if that doesn't work, increase the plasma/cell ratio and if you still can't get 2+ reactions, go to a 1-6 C incubation with controls.  Our computer system has limitation on the reaction strength in the ABORH test, so if we have to result <2+ and call it positive, we have an ABORH discrepancy test that has different rules.

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This is my understanding, maybe it is not correct, just want to share it here, and correction is always welcomed.

If the reverse typing is weak than 2+, it means the immediate spin result, the antiboies are weaker than normal, subgroup or weaken antiglobulin.

Even we incubate or change the reaction temperature or add more serum, it shows 2+ or stronger  reaction, it is still weaker than normal typing( not so exactly, because my Enligh is not good). Can we call it normal when we incubate or 4 degree C treaction 2+, no. These are just ways to strengthen the reaction.  Which is somehow like we do weak D test, can we call it normal D when we get pos result in anti-antiglobulin test.

:):):)

 

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16 hours ago, yan xia said:

This is my understanding, maybe it is not correct, just want to share it here, and correction is always welcomed.

If the reverse typing is weak than 2+, it means the immediate spin result, the antiboies are weaker than normal, subgroup or weaken antiglobulin.

Even we incubate or change the reaction temperature or add more serum, it shows 2+ or stronger  reaction, it is still weaker than normal typing( not so exactly, because my Enligh is not good). Can we call it normal when we incubate or 4 degree C treaction 2+, no. These are just ways to strengthen the reaction.  Which is somehow like we do weak D test, can we call it normal D when we get pos result in anti-antiglobulin test.

:):):)

 

I think of the forward typing as direct test for the patient's blood type, as one is testing for the antigens that define the type (if it works the way it's supposed to with "common" blood types).  Unless one has testing problems with unusual ABO subgroups, the forward typing in most cases will be definitive.

Having said that, the reverse typing normally serves to sort of "confirm" the ABO of the forward typing, as most people will naturally make antibodies for AB antigens they do not have (not detected in the forward typing).

(I agree this is a oversimplification) 

Anyway, the point being that problems with reverse typings are, I think we can agree, much more likely to be due to an artifact related to the testing conditions (e.g. cold agglutinins), or something other than a peculiar blood type (immunocomprimised patients).  The majority of them can be cleared up or accounted for with the various approaches mentioned above, leaving the forward typing as the patient's blood type.

Scott

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15 hours ago, SMILLER said:

I think of the forward typing as direct test for the patient's blood type, as one is testing for the antigens that define the type (if it works the way it's supposed to with "common" blood types).  Unless one has testing problems with unusual ABO subgroups, the forward typing in most cases will be definitive.

Having said that, the reverse typing normally serves to sort of "confirm" the ABO of the forward typing, as most people will naturally make antibodies for AB antigens they do not have (not detected in the forward typing).

(I agree this is a oversimplification) 

Anyway, the point being that problems with reverse typings are, I think we can agree, much more likely to be due to an artifact related to the testing conditions (e.g. cold agglutinins), or something other than a peculiar blood type (immunocomprimised patients).  The majority of them can be cleared up or accounted for with the various approaches mentioned above, leaving the forward typing as the patient's blood type.

Scott

In the case of ABel, the forward typing is not shown B antigens, and reverse typing with weaken anti-B.:)

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and you would - I hope - transfuse with group A, so if you wrongly called it a group A, rather than an AB, it would actually be better for the patient.  I know of at least one case where an ABel was transfused with group AB blood and died as a result of a transfusion reaction.

And if this is a donor, the amount of B antigen present MIGHT cause a minor reaction if transfused to a group A patient but would not do any serious harm.  An what percentage of those weak reactions with B cells will actually be caused by this phenotype anyway?  Probably less than patients having antibodies against LFAs that are not picked up in the antibody screen and who have a minor reaction due to the incredible bad luck of receiving a unit of blood that just happens to have the antigen

 

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I totally agree with you about the transfusion, galvania.

And I think we should call it AB subgroup if there are weak B antigens, rather than A group, because sometimes they will need plasma and something contains plasma.:)

 

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Except that we are talking about patients here that have anti-B in their own plasma already.  We are not talking about patients who have no detectable anti-B in their plasma.  So we are talking about a patient who groups as an A in the forward group and has a ++ reaction in B cells, due to anti-B.  So if he receives group A plasma, yes, he will receive some anti-B - which will be diluted out by his own plasma which already contains anti-B………..

Realistically, I think it is a question of comparing risks, benefits and the amount of work.

In this case, what are the chances that this is an ABwk patient? - Very low

What is the risk, if this patient is an ABwk, of transfusing this patient with group A blood?  None.  On the contrary it is better than transfusing with group AB

What is the risk, if this patient is an ABwk, of transfusing this patient with group A plasma?  very little as the patient already has a considerable amount of his own anti-B in his plasma

What is the risk, if this donor is an ABwk, of transfusing to a group A patient?  Very little as the amount of B antigen present is so small

How much work do you need to do to be 100% sure that this type of reaction belongs to a patient who is really a group A and not ABwk?  As an absolute minimum genotyping, possibly complete sequencing.  Long delays and $$$$$$$$$$$$$$$.

 

 

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Sorry, I am stubborn as for this major, I  guess I have caused noise here.

If the reverse type show antibody then it is ok, why would we call 2+ or more to be normal and less to be weak and then to invest it?

For ABweak patients, I still think it is safe to transfuse them with AB plasma, even they have their anti-B ,but the anti-B is not the same as O and A people's, it is not react with its own B antigens, but the transfused anti-B can, that is why the weak B antigen can be detected with some strengthen method. 

We will identify this kind of weak antigen with add more serum ,4 degree C incubation or adsorption/elution test, not genotype it, which is not so expensive.

 

 

Edited by yan xia
spelling error

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