Anti A1 and Anti B

[Sadique.Kareem]

Hello

I want to know how to check for Anti A and B in neonates for PRBC non O group transfusion.

It is said to include coombs serum while testing. please correct me if i understood wrong .

The way I do is :-

50 ul A1 and B cells in Diamed IgG card + 25 ul of plasma, incubate for 15 min at 37*C and then centrifuge for 10 min.

My concern in this is how can i be sure that i am not catching IgM anti A and B that may be present (rare) in some neonates.

Thanks.

[David Saikin]

IgM does not cross the placenta . . . the neonate should not have any IgM ABO abs (rarely). . . if they do, you want to know anyway.

[Malcolm Needs ☆]

If you want to make sure that the antibodies are maternal (i.e. IgG - David is correct in saying that IgM does not cross the placenta), rather than the baby's own (which would be IgM), you could treat the plasma with dithiothritol to disrupt the J-chain in the IgM molecule, and then perform an IAT using a monospecific anti-IgG reagent.

Seems an awful lot of work to do though.

[R1R2]

I wouldn't worry if you are detecting the baby's own isoagglutinins. You would not give a baby that is group B with anti-A group A blood.

[Sadique.Kareem]

Thanks Malcolm. could you please clarify what is the exact meaning of high titer antibody in group O mothers and how to detect them.

[Sadique.Kareem]

R1R2 yes you are right. Actually i put the question in a wrong way my intention was to know how to detect high titer IgG antibodies in group O mothers.

[Sadique.Kareem]

Thanks david. yes its estableshed fact IgM donot cross placenta but few new borns are seen giving reverse reaction with A1 and B cells. The reason is not clear and I have seen some discusion in our forum ( How Anti A and B are produced) about this issue few months back. I personally came across few new borns 7-10 days of age with these antibodies.

[R1R2]

Thanks david. yes its estableshed fact IgM donot cross placenta but few new borns are seen giving reverse reaction with A1 and B cells. The reason is not clear and I have seen some discusion in our forum ( How Anti A and B are produced) about this issue few months back. I personally came across few new borns 7-10 days of age with these antibodies.

I never say never in blood bank. I think if you can demonstrate an anti A or anti B in a neonate and you have eliminated the possiblity that it came from the mom or a transfusion then you have your answer. In the US, we are not required to routinely test for anti A and anti B until after 4 months of age so we probably don't see this. We do have requirements to test for passive anti A and B in neonates under certain circumstances.

[rravkin@aol.com]

Kareem,

One way to titer Anti A and B would be to serial dilute the mother's plasma in paralell and test against

the A1 and Bcells respectively. This is the same procedure one would use to titer a gestational antibody during the course of pregnancy. The only difference is that you would test with A1 and B cells respectively instead of O type panel cells.

[Malcolm Needs ☆]

Thanks Malcolm. could you please clarify what is the exact meaning of high titer antibody in group O mothers and how to detect them.

I only wish that I could Sadique.Kareem, but there are two problems.

Firstly, nobody seems to agree what "high titre" actually means! Even within the four National Blood Services of Great Britain and Northern Ireland, there is not an agreement as to what this actually means - and when you consider the area of GB and NI compared with the area of the USA, it is a pretty small area in which to agree. Some give a titre of 32, some 128 and others higher.

Secondly, the ABO titre seems to bear no corrolation whatsoever to the degree of severity of haemolytic disease of the foetus and newborn. There is no "titre" that can predict ABO HDFN. The only thing that can be said is that, if a baby has suffered from ABO HDFN in one pregnancy, then the foetus in the next pregnancy will suffer as much, if not more, and at the same stage of pregnancy, if not earlier (assuming of course, that the baby expresses the same ABO group as the eralier baby). That having been said, there are some mothers with really high titre ABO antibodies (over 1000), and their babies never turn a hair.

So, the only way to tell if a baby is likely to suffer from ABO HDFN is from past history - but that does not mean that the second or subsequent baby will not suffer from ABO HDFN, just because a previous baby did not, even if the mother's ABO titre is identical.

ABO HDFN is an enigma, from that point-of-view.

The only thing that I would say is that, if the mother has an IgG titre of 32 or above for an ABO antigen, it should put you on "red alert" to the possibility.

I'm sorry I can't be more definitive.

:confuse::confuse:

[Sadique.Kareem]

Thanks rravkin. But the way you mentioned will detect the mixture of IgM and IgG. Where as we are intrested to know the titer of IgG only. the only way for this it seems is that tedious job of using DTT.

[PAWHITTECAR]

At Children's we titer anti-A and anti-B for newborns that are on the waiting list for possible incompatible heart transplants. There is a cut off for the titre above which they can no longer perform the procedure. Sorry can't remember the cutoff off the top of my head