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Weak Backtype Resolution


RRay

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I'm fairly new to my current institution but noticed some techs are resolving weak backtypes by adding 4 drops of plasma to the A1/B cells and documenting such.  However, this is not an allowance in our policies anywhere. I have a faint memory of this being addressed somewhere in the past about not doing this because if you have to add 4 drops of plasma to detect the AB antibodies, you should do the same in your ISXM and that is very hard to track when you need to do so.  Currently the SOP only allows for an extended RT incubation and a 4C incubation to resolve these missing reactions.

Does anyone have any feedback on this?  Is the plasma being weak an issue for the ISXM?  I mean, that is the whole point... to detect ABO discrepancy.

We are stuck with no electronic XM until mid-late next year.

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Four drops of plasma to resolve back type ABO discrepancies (with an auto control) has been part of procedures in all places I have worked. My concern is that your techs are using a technique that is not part of your labs procedures. 
WRT ISXM: if you resolve the backtype using 4’C (RT) incubation do your procedures require you to do the ISXM at 4’C (RT)?

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Working off of hand-me-down blood bank folklore is a habit I'm having a hard time breaking with my techs.  Pray for me.

Inversely, I've never had the 4 drops procedure in place at any place I've worked.

I follow your logic, but I can't find any recommendation of the 4 drop practice in the Technical standards or methods, or anywhere.  I often wonder how certain practices got started.

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13 hours ago, RRay said:

I often wonder how certain practices got started.

Someone one time tried something once and achieved the results they were looking for and told someone else.......  That's usually how it appears to work and in all my years working in blood banks and transfusion services I have discovered that inertia is the most powerful force in the universe!

:coffeecup:

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I don't feel comfortable adding allowance for the 4 drops procedures for a couple reasons:

-It's against manufacturer's insert, which clearly lists 2 drops of plasma/serum for backtype (I will not bother with validating the 4 drops!)

-I can't find any suggestion for it in the major BB references.

 

@AMcCord Hate to put you on the spot but you referenced this method in older posts (with ISXM provision).  Do you know what the reference is/if any?

 

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This is mentioned as "increasing the serum to cell ratio" in tech manuals and guides, but it is SUPER vague! 

I agree that you should not allow your techs to do this if it's not in the SOP. I have RT and 4C incubations as things to try to resolve blood type discrepancies in my SOP. The only place we mention increased serum to cell ratio is to enhance weak antibody screen reactions by using 3 drops plasma and 3 drops PEG to one drop cells. We don't change serum to cell ratio for blood types or ISXM. 

 

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4 hours ago, Neil Blumberg said:

Let me ask the basic question is this necessary?  If the weak back type agrees with the front type, you know everything you need to safely transfuse the patient.  Why bother with serologic make work?  It has no clinical relevance that I can think of.

If the result is weak, I agree with you.. it is positive.  The situation in question is when it is too weak to detect at IS and how we go about resolving it.

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16 hours ago, RRay said:

If the result is weak, I agree with you.. it is positive.  The situation in question is when it is too weak to detect at IS and how we go about resolving it.

If the problem is that the reverse group is too weak to allow for a safe IS cross-match, DO NOT ALLOW AN IS CROSS-MATCH.  It is simple.

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Instead of fooling around with the back type why not consider doing an anti-globulin crossmatch, or confirming the ABO type of the unit and the patient?

There is no clinical reason to have a stronger backtype if the patient's ABO is clear on repeat samples.  If it is considered important for non-clinical reasons, perhaps do an antiglobulin backtype rather than just arbitrarily increasing the serum to cells ratio, which makes sense but is hard to validate in any convenient way.  Patients with agammaglobulinemia, whether congenital or acquired, may have no isoagglutinins to detect, and it's not worth getting obsessive about it in my view.

Here's another way of looking at this. The absence of isoagglutinins actually makes transfusion safer, as an ABO hemolytic transfusion reaction is very unlikely to occur if there are no detectable anti-A/anti-B.

Edited by Neil Blumberg
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Agree with Neil and Malcolm, might adopt that here! :)

You could have an "antibody", or some other way to require the system to prompt techs, that you add to the patient in your blood bank LIS, which will direct staff to perform an AHG crossmatch. That way, there isn't an antibody actually resulted in the HIS, but the staff will be alerted to the need for an AHG XM rather than relying on them catching that there was a weak backtype. 

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1 hour ago, Neil Blumberg said:

Here's another way of looking at this. The absence of isoagglutinins actually makes transfusion safer, as an ABO hemolytic transfusion reaction is very unlikely to occur if there are no detectable anti-A/anti-B.

I am a little worried about this because, even if there are VERY low numbers of isoagglutinins, if there is a normal level of complement, it can still be extremely dangerous, as there is massive amplification within the complement system (see the excellent attached PowerPoint lecture, written for me by my friend Grant Webb).

The Complement System.pptx

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4 hours ago, Neil Blumberg said:

Instead of fooling around with the back type why not consider doing an anti-globulin crossmatch, or confirming the ABO type of the unit and the patient?

There is no clinical reason to have a stronger backtype if the patient's ABO is clear on repeat samples

Again, the issue at play is that we cannot confirm the patient ABO and the ABO is not clear at initial testing.  We understand that weak positive is positive but the issue is having no reaction at all.  You cannot confirm type with discrepancy present.

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3 hours ago, jshepherd said:

You could have an "antibody", or some other way to require the system to prompt techs, that you add to the patient in your blood bank LIS, which will direct staff to perform an AHG crossmatch. That way, there isn't an antibody actually resulted in the HIS, but the staff will be alerted to the need for an AHG XM rather than relying on them catching that there was a weak backtype. 

Yes! That is the hardest part.  LIS cooperation.  It's hard to notify techs to treat a patient differently.

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"Again, the issue at play is that we cannot confirm the patient ABO and the ABO is not clear at initial testing.  We understand that weak positive is positive but the issue is having no reaction at all.  You cannot confirm type with discrepancy present."

My point is that if the front type is unambiguous and also reproducible on the same sample and on a repeat sample, the back type is almost totally irrelevant clinically.  It's a useful check on the front type, but not indispensable for determining the ABO type. 

As a tertiary care children's hospital we treat infants, children and occasional adults with no detectable isoagglutinins all the time,  and we simply rely on the front type for transfusion, if necessary.  Thus far, no problems in my 42 years here.  

If there is any uncertainty, we use washed group O red cells, which are not available at most hospitals.  Unfortunately the entire field of blood banking/transfusion medicine labor under the convenient but incorrect belief that stored supernatant of red cells and platelets, particularly ABO mismatched, causes no harm to patients.  Randomized trials suggest otherwise.  If it were up to me, every hospital would be required have the capability of removing supernatant from red cells and platelets in select patients.  

Edited by Neil Blumberg
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I'm working from home today, so the AABB standards are not at my right hand, but I'm pretty sure AABB requires a front and back type to be resulted to count as a full blood type for adults. There are exceptions for peds of course. No full blood type means you should be giving type O red cells and type AB plasma, which no one wants to do unless warranted! 

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"No full blood type means you should be giving type O red cells and type AB plasma, which no one wants to do unless warranted! "

 

The AABB standards, if that's what they say, are totally wrong from a clinical perspective and shear bureaucratic rigidity.  If you know the patient's ABO type with total certainty from the front type, the correct and safest transfusions are ABO identical red cells, platelets, plasma and cryo.  We never transfuse antigen positive cells, obviously, in the face of even weak anti-A or anti-B.  But when things are clear and there is no antibody present, ABO identical is the clear clinical imperative.  I always put the patient's best interest before regulatory or accreditation bad advice, and as a physician, that is both my responsibility and authority.  Happy to defend this approach in public, court or any other venue :).

Edited by Neil Blumberg
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4 minutes ago, Neil Blumberg said:

"No full blood type means you should be giving type O red cells and type AB plasma, which no one wants to do unless warranted! "

 

The AABB standards, if that's what they say, are totally wrong from a clinical perspective and shear bureaucratic rigidity.  If you know the patient's ABO type with total certainty from the front type, the correct and safest transfusions are ABO identical red cells, platelets, plasma and cryo.  We never transfuse antigen positive cells, obviously, in the face of even weak anti-A or anti-B.  But when things are clear and there is no antibody present, ABO identical is the clear clinical imperative.  I always put the patient's best interest before regulatory or accreditation bad advice, and as a physician, that is both my responsibility and authority.  Happy to defend this approach in public, court or any other venue :).

I agree entirely with Neil Blumberg (although, of course, as a former Biomedical Scientist, I don't have his legal authority), but there are situations involving adults where the reverse group will not always match the forward group (for example, post certain bone marrow/stem cell transplantation procedures - see, for example, Needs ME, McCarthy DM, Barrett J.  ABH and Lewis antigen and antibody expression after bone marrow transplantation.  Acta Haematology 1987; 78: 13-16, DOI: 10.1159/0002205828, and Hult AK, Dykes JH, Storry JR, Olsson ML.  A and B antigen levels acquired by group O donor-derived erythrocytes following ABO-non-identical transfusion or minor ABO-incompatible haematopoietic stem cell transplantation.  Transfusion Medicine 2017; 27: 181-191.  DOI: 10.1111/tme.12411.) for perfectly natural reasons, and in such cases, we also followed the forward group - at least, after the advent on ABO monoclonal antibodies.

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2 hours ago, jshepherd said:

I'm working from home today, so the AABB standards are not at my right hand, but I'm pretty sure AABB requires a front and back type to be resulted to count as a full blood type for adults. There are exceptions for peds of course. No full blood type means you should be giving type O red cells and type AB plasma, which no one wants to do unless warranted! 

! 5.14.1  ABO Group

The ABO group shall be determined by testing the red cells with anti-A and anti-B reagents and by testing the serum or plasma for expected antibodies with A1 and B reagent red cells. If a discrepancy is detected and transfusion is necessary before resolution, only group O Red Blood Cells shall be issued.

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I can see why they make this recommendation. But it is wrong if one has the ability to be sure that the ABO type is known without doubt (the discrepancy has been resolved by drawing another sample and repeating the front typing, for example).  We have become quite casual in assuming group O red cells are safe as "universal donor."  While this is safest when the ABO is not known, we should never forget this is sub-optimal for non-O patients.  Any therapy that has significantly greater risk than the preferred therapy (ABO type specific/identical) is sub-optimal, and we seem to have forgotten this due to the logistic convenience (and sometimes necessity) to give group O red cells to non-O patients. It can be fatal not to mention impairing the blood supply. 

The absence of isoagglutinins, if anything, makes transfusion safer. 

The use of universal group O red cells in an emergency may make clinical sense, but exposes the patient to potentially fatal (if very rare) hemolysis due to few dozen milliliters of incompatible plasma when transfused to the 55% of patients who are not group O.  To my knowledge, I have never seen or read about a patient whose front typing led to an ABO hemolytic reaction because it was "wrong."  The front typing is immunohematologic gold and clinically critical.  Not so much the back typing which is merely confirmatory. 

Granted that in the absence of technical and medical expertise it may not be possible to execute my suggestions, but we should be aware that following the AABB Standards advice is inferior clinical care if implemented as an absolute, because on occasion it will cause great harm.

Edited by Neil Blumberg
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2 hours ago, Ensis01 said:

I am in the resolve the Backtype at a minimum of once for every patient.  I have had two Bombay phenotype patients in labs I have worked in. 

I have seen numerous cases of Oh, and they all had pretty strong reverse groups, rather than weak or negative reverse groups.

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On 12/6/2022 at 3:31 PM, RRay said:

If the result is weak, I agree with you.. it is positive.  The situation in question is when it is too weak to detect at IS and how we go about resolving it.

If we have a patient w no detectable ABO isoagglutinins our procedure is to perform an ahgxm in addition to the immediate spin.  When I was validating gel we had a few patients w no detectable ABO abs:  they weren't detectable at ahg either.

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Excellent points from Neil and Malcolm as always! Most of us are slaves to the standards though, and/or don't have pathologists willing to take this same point. 

@RRay Lots of food for thought here! I think we will be implementing something similar here, adding an "antibody" to the patient file in the BB LIS only that will require an AHG XM when additional drops of plasma are used to resolve a blood type. 

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