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Passive Antibodies

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Hope someone can clear things up for me:

1. Can a type B recipient have 'testable' anti-B, acquired passively via transfusion of a few type A and type O platelets?? Let's say one out of type per day for a week.

2. Does Type B and Type O persons have naturally occurring Anti-A2??

Inquiring minds want to know, thanks in advance. 

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There is an article from George Garretty called Problems Associated With Passively Transfused Blood Group Alloantibodies that kind of mentions this. Although I feel it is perfectly safe to give out of group platelets, (we have done so for years) my concern was at what point would it interfere, if ever, with ABO/Rh type testing with tube method?  According to the article worst case would be positive DAT but again I wonder if it would be detected in the plasma

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I would tend to agree with George Garratty (who wouldn't!?), but, having seen many cases of out of ABO group transfusions of platelets, FFP and cryoprecipitate, and having studied, as much as possible, there have been very few cases where there have been any clinical problems confined to cases involving very small babies given ABO mismatched platelets, FFP and/or cryoprecipitate, but never children of small stature or adults, and, in these cases, there does not seem to have been any problems ABO typing these patients after the transfusions.

What may be of interest is, I think, a unique report of a case where a patient, with no atypical alloantibodies, who was given two units of blood, one of which was K+, and one of which contained a high titre anti-K, and these two units reacted in the patient's circulation (see attached scan).

Zettner and Bove.docx

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On the topic of passive antibodies, I have a student in transfusion services right now who wants to know why we don't have to respect zygosity when ruling out on an abbreviated panel (Ortho 0.8%) performed when passively acquired anti-D is suspected to be the reason for the positive antibody screen.  I have emphasized the importance of ruling out using zygosity or possibly missing an antibody.  Now with the abbreviated panel I tell them ruling out with zygosity is not necessary.  Anybody have any history on this?

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Thank you Malcolm.  Just to clarify, this abbreviated panel is done only when the prenatal antibody screen was negative and a RhIG shot has been verified as given.

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Ruling out on zygosity....I'm assuming you are referring to "crossing-out" on heterozygous cells, as opposed to homozygous cells, that are nonreactive in Gel testing?

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Well, as a matter of correct nomenclature, I wouldn't put it like that.  Homozygous, heterozygous and hemizygous are terms that should be reserved for genes, and red cells do not contain a nucleus, let alone genes.  However, in terms of antigen expression, I would say homozygous, heterozygous or hemizygous expression, where possible (there are some antigens that show no "dosage" in terms of expression) than can be non-reactive by ANY serological technology.

The Sd(a) antigen, which used to be within the 901 Series of High Prevalence Antigens has just become a blood group system (the SID Blood Group System), but approximately 91% of individuals are serologically Sd(a+), but a further 5% are Sd(a+) when their urine is tested, and only 4% are truly Sd(a-), so this kind of thing must be remembered when you are talking about different technologies and techniques.

It's not easy!

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Forgive my ignorance but what is the positive reaction you get when testing reagent Anti-A  with A2 cells due to??

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Anti-A.

Group A red cells can be sub-classified using Anti-A1 lectin as being A1 or not, the later we call A2.

Edited by Veejay
more info

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I agree with Veejay.

The reaction is with the A antigen, not a fictitious antigen named A2, and so the antibody is anti-A, not anti-A2.

This A antigen is also expressed on A3, Ax, Am and other group A subgroups, not just on A2 red cells, but, importantly, is also expressed on A1 red cells, as is the A1 antigen.

For details, see the attached PowerPoint.

What is the difference between A1 and A2.pptx

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Thank you all but I still can't find a reference for acceptably using an abbreviated panel (Ortho 0.8% panel) to rule out other clinically significant antibodies on the panel when passively acquired Anti-D is suspected (i.e. a negative antepartum antibody screen and documented administration of RhIG)

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10 hours ago, jnadeau said:

Thank you all but I still can't find a reference for acceptably using an abbreviated panel (Ortho 0.8% panel) to rule out other clinically significant antibodies on the panel when passively acquired Anti-D is suspected (i.e. a negative antepartum antibody screen and documented administration of RhIG)

We don't use just the cells that Ortho marks as an abbreviated panel for ruling out other specificities in the presence of passive anti-D.  We add whatever other cells are required to have double-dose expression of the usual suspects.  That said, we don't require double-dose K for ruling out anti-K on antibody screens so would not require it here.  Also, we don't require use of double-dose E or C positive cells in the presence of anti-D, whether passive or immune, due to the low statistical risk to the patient.

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I think you have to rule out C and E using r'r and r"r cells.  Only very rarely does one find r'r' and r"r" cells (probably reference labs have some frozen). 

When you are r/o anti-D due to RhIg injection I guess you can go with single dose ag strength.  I adjust my anti-RhIg panel to include double ag doses whenever I can, except for C and E.

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On ‎12‎/‎3‎/‎2019 at 6:24 AM, jnadeau said:

Thank you all but I still can't find a reference for acceptably using an abbreviated panel (Ortho 0.8% panel) to rule out other clinically significant antibodies on the panel when passively acquired Anti-D is suspected (i.e. a negative antepartum antibody screen and documented administration of RhIG)

Whether it is acceptable or not is a lab/lab director decision.   There are no regs that prohibit the practice.   Your policies should address using an abbreviated panel.   

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1 hour ago, David Saikin said:

When you are r/o anti-D due to RhIg injection I guess you can go with single dose ag strength.

Sadly, it is not that easy.  It is incredibly rare for an anti-D to show dosage, however, there can be noticeable differences in the strength of expression of the D antigen, even between individuals with the same Rh phenotype and, indeed, genotype.

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46 minutes ago, Malcolm Needs said:

Sadly, it is not that easy.  It is incredibly rare for an anti-D to show dosage, however, there can be noticeable differences in the strength of expression of the D antigen, even between individuals with the same Rh phenotype and, indeed, genotype.

Except that you don't have much choice to r/o anti-C or anti-E but r'r and r"r cells.   We're talking RhIg anti-D, which is usually 1+ in gel

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On 12/4/2019 at 6:24 AM, Malcolm Needs said:

Sadly, it is not that easy.  It is incredibly rare for an anti-D to show dosage, however, there can be noticeable differences in the strength of expression of the D antigen, even between individuals with the same Rh phenotype and, indeed, genotype.

This is why we treat all those weakly reacting anti-D patients as though the screen is negative and give them RhIG.  It is safer even if the antibody is really a newly forming anti-D.  Most of these are detected at the time of delivery so this baby is not at much risk from an immune anti-D of that low a titer.  If the baby has HDFN, then we will proceed accordingly.  If we pick up a weak anti-D and the patient received RhIG in the prior months but there is no record of a negative screen before the RhIG was given we will sometimes follow the patient for a few months to make sure the titer is decreasing rather than rising.  We even have a test called SAB Rh Type that is for an Rh type and reflexes an antibody screen if the Rh is negative.  That way we have a baseline antibody screen before RhIG is given which increases the odds that the anti-D detected later is passive.  

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Agree entirely David (apart from the fact that antigens and cells cannot be homozygous, heterozygus or hemizygous, only genes can be termed as such).

In the UK, of course, we do an enzyme panel in most cases, but I do agree that, in reality, r'r' and r"r" red cells are, in reality, only available to Reference Laboratories, and only then used sparingly (not least because antibodies that are that weak are rarely, if ever, clinically significant, either for HTR's or HDFN).

My point, however, was that, from a serological point-of-view, unless you can perform Gm and Km typing of the antibodies, you cannot tell the difference between a passive anti-D and a weak allo-anti-D (and even that is not 100% reliable), you HAVE to rely on the patient's history as to whether or not she has been given prophylactic anti-D immunoglobulin, and whether or not there was any evidence of allo-anti-D in her circulation before she was given any prophylactic anti-D immunoglobulin.

Edited by Malcolm Needs
Noticed a typo ("ws" instead of "was").

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Thank you ALL for your insightful posts - my student is a little overwhelmed with some of the replies (and might be sorry she asked) but she's very sharp and also appreciates your expertise - it's led to some thoughtful discussions here.  Since we would have a negative antibody screen performed shortly before they would give a RhIG shot and since we "rule out" some antibodies without respect to dosage when performing an antibody screen I think we'll continue with the abbreviated panel in these instances.  Happy Holidays to you all. 

 

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19 hours ago, Malcolm Needs said:

 

My point, however, was that, from a serological point-of-view, unless you can perform Gm and Km typing of the antibodies, you cannot tell the difference between a passive anti-D and a weak allo-anti-D (and even that is not 100% reliable), you HAVE to rely on the patient's history as to whether or not she has been given prophylactic anti-D immunoglobulin, and whether or not there was any evidence of allo-anti-D in her circulation before she was given any prophylactic anti-D immunoglobulin.

Agree entirely

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On 12/6/2019 at 3:57 AM, Malcolm Needs said:

 

My point, however, was that, from a serological point-of-view, unless you can perform Gm and Km typing of the antibodies, you cannot tell the difference between a passive anti-D and a weak allo-anti-D (and even that is not 100% reliable)

Malcolm, may I ask what is Gm and Km, and why typing those can tell us if the  one is passive or allo-anti-D? Thank you .

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