Cord Blood DAT workup?

[NB883]

It has been suggested to me to just report out that the Cord Blood DAT is positive, and not to take it any farther without phsician request. I want to know what other labs do and what other blood bankers think about this.

[Deny Morlino]

What you are considering is the way our policy works. DAT's for cords are reported as positive and it is up to the physician whether they wish to pursue further testing or not. Normally they treat the patients with supportive measures including lamp banks. If the baby is in an extreme state they are transferred to a larger facility specializing in children about an hour away. This blood bank pursues their own workup obviously. Has been this way for at least 20 years here. Hope this helps.

[bmalon3]

If the DAT is positive we call to notify the nurse or doctor and do not pursue any farther.

[adiescast]

If the mother is a different type from the baby without other antibodies, we have a comment stating that it is probably due to ABO mismatch with Mom. If the mother has other antibodies, her type matches the baby, or we don't know her history, we do an elution to try to find the source of the positive DAT.

[Malcolm Needs ☆]

As a Reference Laboratory, when we get such samples (which is not often I have to say), we pull out all the stops and do every test under the sun, particularly if the baby has a positive DAT, the mother has no known antibodies and the ABO groups are compatible.

This is just in case there is an antibody present directed against a low incidence antigen inherited from the father (can't think of how else to put this - I know antigens are not inherited; only genes are inherited, but you know what I mean). This would include having a sample from the father of course, which is not always easily available (sometimes, of course, the father is not even known).

This is purely to give a "heads up" for any future pregnancies.

Apart from this, I would agree with others. I wouldn't go too much further in almost all cases.

:):)

[NB883]

As a Reference Laboratory, when we get such samples (which is not often I have to say), we pull out all the stops and do every test under the sun, particularly if the baby has a positive DAT, the mother has no known antibodies and the ABO groups are compatible.

This is just in case there is an antibody present directed against a low incidence antigen inherited from the father (can't think of how else to put this - I know antigens are not inherited; only genes are inherited, but you know what I mean). This would include having a sample from the father of course, which is not always easily available (sometimes, of course, the father is not even known).

This is purely to give a "heads up" for any future pregnancies.

Apart from this, I would agree with others. I wouldn't go too much further in almost all cases.

:):)

Thanks! I always want to find an answer. It is difficult to just leave it as positive. But in most cases it isn't really all that important to investigate it. In almost all of our cases the baby is fine and the source of the problem is gone.

[Deny Morlino]

By the way NB883 welcome to BBT. Missed that you were new before I left for vacation.

[Lori McClintock]

That is what we do at our Hospital. The only cord blood DAT's we do are on babies born to O mothers or Rh neg mothers. When we get a positive DAT, we call the Nursery, usually they have us send the cord blood for a Bili and that's it.

[YorkshireExile]

We only do cord bloods on group O mothers and Rh Neg mothers. If the DAT is positive we send the cord blood for a bili. We simply report DAT positive due to maternal anti - whatever. No need for elutions as 99% of the time it will be obvious what is causing the pos DAT

[BBK710]

If the mom is type O and the baby is A or B we do an antibody screen (on the mother) if it is negative we report that the DAT is positive and probably due to ABO incompatibility. If the mom's antibody screen is positive we don't add the comment and it is up to the physician to order addtional testing.

[LAURAA80]

We perform cord blood ABO's on mothers that are Group O and all Rh- mothers. In our current procedure, we are to reflex DAT testing on all ABO incompatibilities. In practice, through the years, we began doing DAT on any ABO and Rh differences between mother and baby. If the DAT was positive, it was reported and an elution is always run. We report out as Maternal Anti-__. Our problem is enforcing the current procedure. If there is an A- mother with an A+ baby, we would relfex the DAT. Now we are looking into this and not thinking it's necessary, especially when the mother has anegative antibody screen. What if the mother has rhogam...is there a valid reason in performing the DAT? It is my understanding rhogam does not cross to baby. If there was an instance where a mother had a true antibody, we would do a DAT on baby for sure. I'm interested to hear what others are doing about Rh differences.

[vam3401]

We also just report out the Cord Blood's DAT as positive. If requested by the physician, we will do further testing.

[NB883]

RhoGAM does have the ability to cross the placenta, and can cause a weak positive DAT, especially if you use the gel method. It is a low titer and not harmful to the baby. We recently had a case where this has happened.

[AMcCord]

I've also seen pos DATs on babies due to RhoGAM. It's always been weak, but definitely there.

[Sfdreams]

So interesting to see the different ways everyone handles this!

We do cord blood workups on whatever cord bloods are sent down (usually from O moms or Rh neg moms, but occasionally others). If the DAT is positive, this is considered a critical result and phoned to the nursery. If the mom is O positive (which is usually when we get a positive DAT on a cordblood) we do a modified Du procedure, where we test the cord serum with A or B cells (whichever the baby is) and O cells. If it is positive after incubation/washing/and adding IGG coombs, we report the presence of anti-A (or in baby's serum.

I haven't seen a positive DAT on a cord from an Rh neg mom, but I did at my previous employment in CA. Our policy here is to perform a panel on cord serum if DAT is positive on cords with same type as mom, and on different type mom's as well as the ABO incompatibility screen if mom has a history of an antibody.

[Sfdreams]

Positive DAT

↓

Look up mother’s blood type in HBB

(or call the floor if no Hx in computer)

↓

Mother ABO Compatible?*

↓ ↓

Yes No

↓ ↓

Hx of Maternal Antibody? Hx of Maternal Antibody?

↓ ↓ ↓ ↓

Yes No Yes No

↓ ↓ ↓ ↓

Spin cord blood and Spin cord blood Spin cord blood Perform ABO

Perform antibody ID and perform antibody and perform antibody incompatibility

on cord serum. ID ID on cord serum. identification on cord screen. Report

should correspond to If antibody is identified, serum. Perform ABO antibody

mother’s antibody. request a sample from incompatibility screen present.

Report antibody the mother and verify also. Report antibody

present. antibody. Report present.

antibody present.

[Sfdreams]

Sorry about this post!! Should have checked preview before posting! The formatting held until I posted the reply!!

[DPruden]

We only do cord blood workups on Rh negative mothers and any other cord that is requested by the physician. If we have a positive DAT and there is an ABO incompatibility, we append a comment that the DAT is presumbaly due to the ABO incompatibility. I attached our flowchart.

Cord DAT flowchart.doc

[profbaud]

If you know the Mother's blood type and she has a Negative AB screen, and you are able to conclude that the positive DAT is due to an ABO incompatiblity, then yes that's all the farther you need to go. If the Mother has a clinically significant alloantibody, then an eluate needs to be performed to confirm that Baby has HDN due to that antibody and not an ABO incompatibility

[Malcolm Needs ☆]

If you know the Mother's blood type and she has a Negative AB screen, and you are able to conclude that the positive DAT is due to an ABO incompatiblity, then yes that's all the farther you need to go. If the Mother has a clinically significant alloantibody, then an eluate needs to be performed to confirm that Baby has HDN due to that antibody and not an ABO incompatibility

I would agree entirely with what you say, particularly as some babies have unexplained positive DAT's, whilst those with a DAT caused by maternal ABO antibodies often develop symptomatic HDN after they have left hospital. If the mother is unaware of this danger, this could be much more serious, or even fatal.

:eek::eek: