cord testing when mom has antibody

[alanh1954]

If an O pos mom has an antibody, let's say a Fya, and delivers an A pos baby, I would do a DAT on the cord and Fya and Fyb antigen typings on it as well. Additionally, if the DAT was positive on the cord, I would do an eluate on it, too, to see if it's Anti-A or Anti-Fya coating the cells.

But as we discussed this today in the lab, I realized that I may be doing more work than is really necessary. Polling our coworkers revealed that everyone is approaching this a little differently, and there is nothing in our procedure manuals that says we have to anything more than a DAT on the cord and do electronic crossmatches with Fya negative red cells if transfusion is required. However, a lot of us remember doing all of the above "in the old days" (20 something years ago!) and wonder if this is another one of those things that fell into the category of being no longer necessary.

[YorkshireExile]

We wouldn`t bother doing an eluate. We would just report the DAT as positive and give Group O positive, Fya negative cells if required. I`m all for reducing the workload!

[Malcolm Needs ☆]

I'm with you alanh1954.

It may be a little "over the top", but I would rather be safe than sorry.

Both anti-A and anti-Fya tend to cause haemolytic disease of the newborn, rather than haemolytic disease of the fetus, and both can be delayed. I would rather be prepared if blood were to be needed in an emergency (e.g. a flat baby coming back into the hospital after being taken home).

Mind you, I would have performed Duffy typing on the dad prior to delivery, just to see if the baby was likely to inherit the FYA gene, as the mum may have made the anti-Fya as a result of the transfusion. Then, if the baby had a positive DAT, I would suspect maternal anti-A, but would also be a bit wary of the mother having made an atypical alloantibody against a low incidence antigen carried by the dad (in other words, if at all possible, I would adsorb the eluate with another group A cell, and then test it against the dad's red cells, if at all possible).

That all having been said, I work in a Reference Laboratory, where we do everything to the nth degree. If I were working in a busy hospital, I could well think very differently!

[clmergen]

Malcolm, don't forget the daddy's are not always in the picture. We are doing intrauterine transfusions on a baby and have NO idea of the dad's typings.

But we always do a DAT on the cord blood of a mom with an antibody. Eluates are up to the doctor.

[Malcolm Needs ☆]

Malcolm, don't forget the daddy's are not always in the picture. We are doing intrauterine transfusions on a baby and have NO idea of the dad's typings.

But we always do a DAT on the cord blood of a mom with an antibody. Eluates are up to the doctor.

True, but I did say "if at all possible".

[RR1]

The baby needs to be treated on the basis of their symptoms. If the mum is known to have an antibody and the DAT is pos, then the paediatricians need to monitor adequately.

Eluates are a load of 'flaff' for a hospital blood bank to perform, (this word was explained in a previous thread). What exactly is it going to show you in terms of transfusion requirements for the babe?

[Mabel Adams]

Stated paternity is not always reliable--especially if purported father is in the room when the question is asked.

Fy typing must have been done with cells treated to remove the antibody or the pos DAT would give false pos results. Or has someone made a monoclonal for Duffy typing that I don't know about?

We need to know how to transfuse this baby but we may sometimes want to know what might affect a future baby as well. Finding anti-A on the A cells of a baby born to an O mom doesn't tell you much. It's absence would rule out anti-A as a cause, but many O moms make some IgG anti-A,B that can be eluted off the baby's cells or found in the cord serum even though it doesn't cause any jaundice or sometimes even a positive DAT.

[Malcolm Needs ☆]

Stated paternity is not always reliable--especially if purported father is in the room when the question is asked.

Fy typing must have been done with cells treated to remove the antibody or the pos DAT would give false pos results. Or has someone made a monoclonal for Duffy typing that I don't know about?

We need to know how to transfuse this baby but we may sometimes want to know what might affect a future baby as well. Finding anti-A on the A cells of a baby born to an O mom doesn't tell you much. It's absence would rule out anti-A as a cause, but many O moms make some IgG anti-A,B that can be eluted off the baby's cells or found in the cord serum even though it doesn't cause any jaundice or sometimes even a positive DAT.

I agree with (almost) everything you say here Mabel.

The only slight disagreement I might have with you is in the predictive nature of any anti-A that might be eluted. Whilst I would totally agree with you that titration of IgG anti-A (or anti-B come to that) is a waste of reagents, time and money, if the index neonate is affected in any way by the maternal IgG anti-A (albeit subclinically), the next and subsequent group A babies borne by the same mum will be affected at least as much as the first, if not more so, and at the same gestation period or earlier, so its demonstration does alert the neonatologist to watch for potential problems in future pregnancies.

I also agree that the DAT due to ABO IgG antibodies can often be negative at birth, but equally as often, the DAT becomes positive after a couple of days. To "get ahead of the game", so to speak, it is sometimes worthwhile putting the cord sample in a fridge for a couple of hours and then examining it macroscopically for agglutination. IgG ABO antibodies can cause agglutination, and this agglutination is sure as hell not going to be caused by a "normal" maternal "cold" agglutinin, such as anti-I, anti-HI, etc.

Just a thought.

[L106]

In response to alanh1954's orginal posting, our institution routinely orders ABO/Rh and Direct Antiglobulin Test on every newborn. (I don't think it's necessary on every newborn, but that's what our pediatric/neonatolgy staff wants.)

So, we do ABO, Rh, and DAT on every baby. If the DAT is Positive, we perform an elution to identify the antibody causing the Pos DAT. (If we find Anti-Fya in the eluate we have indirectly proven that the infant is Positive for the Fya antigen, so we wouldn't bother to worry about trying to clean the antibody off the baby's red cells to perform an Fya antigen typing on the baby's red cells.)

Even though an elution may not be "required", I would prefer do the workup and document the findings now while I have the sample at hand, rather than try to put the pieces of the puzzle together a few years down the road when she's pregnant again and the OB/GYN calls and asks questions about what the problem was with her last baby, etc.

Edited July 9, 2009 by L106
Spelling correction (ie: Malcolm's typical reason)

[Malcolm Needs ☆]

I agree with you L106; performing a DAT on all cord samples is extremely excessive.

You are quite right that, if anti-Fya is eluted (as long as the last wash control is negative) then there is no need to treat the baby's red cells and then group them.

But I really agree with you wholeheartedly about the fact that I can't spell!

:D

[JOANBALONE]

Back to the original post, we would perform AHG crossmatch using antigen negative blood and mom or infant plasma.

[RR1]

In a situation where the baby would require an exchange transfusion, is performing an eluate actually going to make a difference to the blood selected for this? - No.

I would use group O, Fya- .

In an urgent situation would you delay blood provision until you had the elution results ?.

I hope not.

Edited July 9, 2009 by RR1

[katrap]

My primary worry with the electronic crossmatch aspect is that the mother, obviously an antibody builder, is forming another antibody that is not readily detectable in her serum, because it has virtually all attached to the fetal cells. I would do an eluate, just to be sure there's no antibodies other than the Anit-A and Anti-Fya attached to the baby cells.

[Malcolm Needs ☆]

My primary worry with the electronic crossmatch aspect is that the mother, obviously an antibody builder, is forming another antibody that is not readily detectable in her serum, because it has virtually all attached to the fetal cells. I would do an eluate, just to be sure there's no antibodies other than the Anit-A and Anti-Fya attached to the baby cells.

Coming from someone who would do an eluate (explanation as to why above) I'm not absolutely sure that I agree with your reasoning katrap. I know that sounds stupid, but this is the reasoning.

If the antibody cannot be detected in the maternal plasma, the titre is going to be incredibly low. Now, knowing that the transport of IgG antibody is an active, rather than passive transport, the concentration of said antibody is going to be higher in the baby's circulation, than in the mother's. However, as you say, all of this antibody will be on the foetal red cells (in other words, the baby's red cells are already sensitized) and there will be very little of this de novo antibody in the baby's plasma.

As this antibody will have been made in the third trimester, quite apart from the fact that it is at a low concentration, it is most unlikely to cause HDN. But, in addition, it is most unlikely to cause a haemolytic transfusion reaction in the baby, either when the baby receives a top-up transfusion, or if the baby receives an exchange transfusion (even less so, in the latter case, as the antibody will be removed by the exchange).

All that having been said, as a reference worker, as opposed to a hospital worker, I would still do an eluate.

Sorry to be so contrary!

[RR1]

In an urgent situation would you delay blood provision until you had the elution results ?.

I hope not.

I presume by the lack of a response to my question, that elutions are not being performed prior to blood being made available for the baby.

I know elutions are interesting (and fun) to perform, but in the case of HDN - really how relevent are they. What information do you actually obtain, that could not have been worked out by looking at maternal group and screen results?

[Malcolm Needs ☆]

I presume by the lack of a response to my question, that elutions are not being performed prior to blood being made available for the baby.

I know elutions are interesting (and fun) to perform, but in the case of HDN - really how relevent are they. What information do you actually obtain, that could not have been worked out by looking at maternal group and screen results?

I would be completely gobsmacked if people performed eluates prior to giving blood in an emergency situation, and I am not necessarily saying that eluates should be performed prior to even a "cold" transfusion.

What I am saying is that, if an eluate is performed at some time (preferably whilst the sample is still in date!) it can have a predictive value for the next or subsequent pregnancy. I'm not suggesting that people go overboard about this in terms of timing.

[RR1]

Thanks Malcolm, but why can't you give a prediction on the next pregnancy based on the clinical outcome of the present baby? After all, we can't even guarantee paternity will even be the same next time. I don't recall ever being asked for the elution results of any affected case in the last 25yrs.

We are all under staff and time constraints so it's good to question practices we have always performed (or not) to see if we can eliminate the unnecessary ones or improve current ways of working. .

[Malcolm Needs ☆]

Thanks Malcolm, but why can't you give a prediction on the next pregnancy based on the clinical outcome of the present baby? After all, we can't even guarantee paternity will even be the same next time. I don't recall ever being asked for the elution results of any affected case in the last 25yrs.

We are all under staff and time constraints so it's good to question practices we have always performed (or not) to see if we can eliminate the unnecessary ones or improve current ways of working. .

You can't predict severity, for the simple reason that the rule of thumb is, if the next or subsequent baby inherits the gene that leads to antigen expression, the baby will almost certainly have the same degree of haemolytic disease as the index case (or worse) and that the baby will be affected at the same stage of pregnancy (or earlier). You can, however, flag up a potential problem.

It is very rare for a baby to be affected less or at a later stage of the pregnancy, unless there is intervention (not necessarily an IUT, by intervention I mean some way of bringing down the antibody concentration, such as IVIG).

I agree that you are under both staffing and time constraints, but we would be happy to perform the tests for you.

Although you may not have been asked for elution results in the past 25 years, I am prepared to bet that, onoccasions, if the clinicians had actually understood what they meant, they would have asked for the predicitive value (particularly in the case of a "new" antibody, or, more importantly, an ABO antibody), however rare this may help.

Edited July 13, 2009 by Malcolm Needs

[RR1]

Hi Malcolm,

But sending to a ref lab will be additional expenditure, and what would we gain from this?

Using the previous example of Cord group A, Mum group O, anti-Fya, the eluate will tell you there is either antii-A or anti-Fya (or both) causing the DAT to be positive. If you can't elute one of the antibodies this would mean either the antibody was at sub-optimal detection leveles or this was not the cause of the positive DAT,but probably the other antibody was.

How exactly will this information improve patient care during subsequent pregnancies, what would the clinicians do differently if they had the actual serological results rather than assumptions?

[Malcolm Needs ☆]

Hi Malcolm,

But sending to a ref lab will be additional expenditure, and what would we gain from this?

Using the previous example of Cord group A, Mum group O, anti-Fya, the eluate will tell you there is either antii-A or anti-Fya (or both) causing the DAT to be positive. If you can't elute one of the antibodies this would mean either the antibody was at sub-optimal detection leveles or this was not the cause of the positive DAT,but probably the other antibody was.

How exactly will this information improve patient care during subsequent pregnancies, what would the clinicians do differently if they had the actual serological results rather than assumptions?

No, no Rashmi, just slip me a gentle back-hander! Won't cost you nearly as much. Whoops, perhaps I shouldn't have said that in public!

Well, in the case quoted, for example, if there was an atypical alloantibody directed against a high incidence antigen, that could only be detected in the eluate, it is not that the clinicians would do anything differently, but we would at the Reference Laboratory.

Say, for example, it were to be an anti-k. There is a fair chance that, by a second or subsequent pregnancy, the anti-k would have reached a titre (not too high, I might add) that would require an IUT. We would organise a steady stream of K+k- donors to be bled, so that there was always fresh K+k- blood on hand for the IUTs, and so there would be cover at birth for both mum and baby.

Okay, this is a bit of an extreme example, but it is not necessarily what the clinicians do, it is what we do to prepare the correct donations in advance.

We have, for example, got three cases of anti-U in pregnancy going at the moment, and believe you me, it is not easy to organise donors for these, so that there are fresh units around when they are due. It takes a lot of juggling, because some donors don't turn up, sometimes the bleed goes wrong (too long, or insufficient), and so we always have to "over-order donors", as it were, to keep one step ahead.

The same problem arises when the antibody is not so rare, but there are a combination of more common maternal antibodies. Even if the baby does not express all the corresponding antigens, the maternal antibodies will still be in the baby's circulation, and could cause a nasty transfusion reaction.

We have to be prepared.

[galvania]

Of course, there's always the problem that mum's antibody screen might be negative completely because dad's got a 'private' antigen not present on the screening cells and passed it on to the baby.

Or mum might have a nice fat juicy antibody, with another one hidden - abnd it's the hidden obne that is actually causing the problem.

'Never do things simply if there's a more complicated way..........'

[Malcolm Needs ☆]

Exactly my point, Anna.

In fact, either last year or the year before, we had exactly that kind of case from one of our large teaching hospitals. We still don't know if the antibody was within the Rh, Diego or Dombrock Blood Group Systems, but we are now warned should the couple have another baby.

Edited July 13, 2009 by Malcolm Needs

[RR1]

Of course, there's always the problem that mum's antibody screen might be negative completely because dad's got a 'private' antigen not present on the screening cells and passed it on to the baby.

Or mum might have a nice fat juicy antibody, with another one hidden - abnd it's the hidden obne that is actually causing the problem.

'Never do things simply if there's a more complicated way..........'

Well, this then leads us having to perform DATs on every newborn...just in case. I can understand performing eluates if baby is DAT pos, with no identified maternal antibodies but the rest is 'over the top'.

Edited July 13, 2009 by RR1

[Malcolm Needs ☆]

Well, this then leads us having to perform DATs on every newborn...just in case. I can understand performing eluates if baby is DAT pos, with no identified maternal antibodies but the rest is 'over the top'.

Um, why?

You need only perform a DAT on those babies whose mother has a known antibody, or on baby's who are showing clinical signs of haemolytic disease. Then, if the DAT is positive, you perform an eluate.

What you've said above Rashmi is not the logical conclusion to be made from Anna's statement.

[RR1]

Yes, I see- thanks!

And how would you handle the 10% or so DAT positive cord samples due to antenatel prophylaxis? I presume you are going on clinical signs.