Weak D testing

[dhil]

Sorry, I bet this is posted somewhere already, but I am under the gun and don't have time to search. We are debating only doing weak D testing on cordblood samples/newborns. We recently had an issue with a pregnant woman who typed as Rh negative Du negative and 10 weeks later Type Rh negative Du positive. Needless to say the physicians are confused and the patient is concerned and ******. The REd Cross verified the positive Du. We are moving towards classifying all Du positive patients as Rh negative. My question is, are other facilities doing this same practice of weak D testing on only cordblood/newborns if the mother is at risk for sensitization? AABB states that is when it is only necessary. Thanks,

Oh yeah, we are still in the stone age with manual tube testing.

[Deny Morlino]

We only perform weak D testing on cord blood/infants. Small hospital (110 bed), no donor collections here.

[kmh76]

We only do weak D testing on Newborns up to 4 months old. We had an issue where a Du positive mother did not get RHIG and produced Anti D. She was a partial D. (She lost the baby) Ever since that happened 3 years ago we decided to call all Rh negative ( on immediate spin) prenatals Negative. Better to be safe then sorry.

[David Saikin]

We do weak D on babies and donors.

[kmh76]

We only do babies as we do not collect donors.

[Malcolm Needs ☆]

Just to complicate matters (as I love to do), there was a poster at the recent BBTS ASM in Bournemouth entitled:

"Expression of the D Antigen Increases on R2r Red Cells during Pregnancy",

By Kumpel B and Wreford-Bush T. (Transf med 2010; 20 (suppl 1): 30 (abstract).

In this, Belinda begins by saying,

"Rarely, pregnant women have changed from D negative at booking (10-16 weeks gestation) to weak D positive at 28 weeks, causing problems for technical staff and clinical management of the patient. This phenomenon suggests that D antigen levels may increase during pregnancy."

Just thought that I would throw that in to muddy the waters!

:blowkiss::blowkiss:

[dhil]

just to complicate matters (as i love to do), there was a poster at the recent bbts asm in bournemouth entitled:

"expression of the d antigen increases on r2r red cells during pregnancy",

by kumpel b and wreford-bush t. (transf med 2010; 20 (suppl 1): 30 (abstract).

In this, belinda begins by saying,

"rarely, pregnant women have changed from d negative at booking (10-16 weeks gestation) to weak d positive at 28 weeks, causing problems for technical staff and clinical management of the patient. This phenomenon suggests that d antigen levels may increase during pregnancy."

just thought that i would throw that in to muddy the waters!

:blowkiss::blowkiss:

gee...thanks!!!

[KKidd]

We only perform weak D testing on Cords/Newborns. However, we did have an instance where a patient claimed that we had typed her wrong. As a result we have a statement that goes on every blood type report "Weak D (Du) testing is no longer performed in compliance with The Joint COmmission and AABB standards." That's a COA for us in the future. It's impossible to explain the complexities of the Rh system to a physician much less a lay person. Good Luck!

:boogie::fingerscr:fingerscr:fingerscr

[AMER]

We do for both of them

[Malcolm Needs ☆]

It's impossible to explain the complexities of the Rh system to a physician much less a lay person.

WIth all due respect to some VERY good physicians, I sometimes think it is harder to explain to many physicians than to lay people, on the grounds that "a little knowledge can be a dangerous thing".

I have every respect for the intelligence of anyone who can become a physician, with all the years of studying and long hours they put in, but there are a few who think that they can be masters in all aspects of medicine, and that is just impossible.

[galvania]

I think that sometimes just explaining to them that the Rh system is extremely complex, that our knowledge of this system is growing, and guidelines are changing to account for the current knowledge, but are in a state of flux because that knowledge is changing often helps them to accept things a bit better

[Malcolm Needs ☆]

Good point Anna.

[rravkin@aol.com]

The only thing that concerns me about the practice of IS Rh-Neg; which in of itself is not a bad practice; however I have observed the practice of administering RhoGam without performing the ABSC. I would think that this practice would complicate our ability to titer an allo D, if it were demonstrated, and therefore obstruct the physician's ability to judge the need for interuterine transfusion.

[Malcolm Needs ☆]

The only thing that concerns me about the practice of IS Rh-Neg; which in of itself is not a bad practice; however I have observed the practice of administering RhoGam without performing the ABSC. I would think that this practice would complicate our ability to titer an allo D, if it were demonstrated, and therefore obstruct the physician's ability to judge the need for interuterine transfusion.

I see from where you are coming in theory, but, in practice, the amount of anti-D immunoglobulin that is normally given, even if 1500IU is the dose administered, would not be enough to make a substantial difference to the level of anti-D in the mother's circulation (although, I must agree entirely with you that it is bad practice not to undertake an ABSC).

In addition though, any decent Obstetrician would not contemplate an interuterine transfusion solely on the basis of the anti-D level. He or she would take into account MCA Doppler/ultrasound readings and various other physiological parameters, in addition to the anti-D level (I HOPE!).

:):)

[bduff]

We only do weak D testing on babies.

Edited October 1, 2010 by bduff
correct wording...

[rravkin@aol.com]

I see from where you are coming in theory, but, in practice, the amount of anti-D immunoglobulin that is normally given, even if 1500IU is the dose administered, would not be enough to make a substantial difference to the level of anti-D in the mother's circulation (although, I must agree entirely with you that it is bad practice not to undertake an ABSC).

In addition though, any decent Obstetrician would not contemplate an interuterine transfusion solely on the basis of the anti-D level. He or she would take into account MCA Doppler/ultrasound readings and various other physiological parameters, in addition to the anti-D level (I HOPE!).

:):)

You are absolutely correct in that the titer of allo D would be but one peice of an overall set of data.

[Barbarakym]

I have worked in a hospital that dropped the Du test 2 years ago. Where I am now supervisor I am also doing this. The AABB guidelines even recommend rhogam for Du positive women due to mosaic. Only requirement is Du on neonate who types NEG by IS (immediate spin or direct method) who is from a mom who is Rh Neg (for rhogam puproses).

Rather than confuse everyone what was done at my previous hospital: We do IS only. If Rh negative everyone is called Rh Negative without doing a Du test. Exception is neonate of Rh negative Mom who also types Rh Neg. We do Du. If baby then proves to be Du Negative baby is called Negative, of course. IF baby types Du Positive, the baby is called Du Inconclusive. Which is a term we called those babies who were Du tested with a positive DAT which interfered with the result. This way while they are in-patients they are handled as if they are D typing unknowns (IE: Mom gets rhogam)...but when they come back at an older age they get the IS only treatment and are typed and archeived as the negative Rh our policy states they are.

We have a canned comment for those folks that were originally called Rh Positive....stating that we have updated our reporting methods and these people will from now on be designated Rh neg or positive by direct test method. Due to increased sensitivity over the last decade or two of reagents, many previously Du positive people now type as positive by direct tests. We use this same comment for these people.

There is still an issue however, Provue (and maybe other machines) are very sensitve to Rh D and call people positive who are not so by IS. Our policy says that any Rh of 2+ or less on the machine needs to have a IS done. And final determination is by IS.

Most of our doctors offices use the direct method and thus these results more often complement them and confuse them less.

Kym

Edited October 4, 2010 by Barbarakym

[LABLAD42]

When we started testing with the Echo we encountered that a few weak D would test as negatives

since the Echo use both series 4D and 5D for testing and found communication from Immunor that required further manual testing of the Rh negatives,manualy,Previously we did`nt have such problems with the Monoclonal D Blend done manualy.

However by using the alternative D(more expensive) on the negatives, and or incubating with Monoclonals Blend at 37.

We are able to confirm the weak D previously missed. Physican education should be an important ongoing processs.

Unfortunately admistrative priorities seems to be in the direction of profit vs qualiy these day...

[Barbarakym]

So you are saying you want to find weak D patients? Why? Do you call then Positive and treat them as Positive?

[rravkin@aol.com]

BarbaraKym,

How are you resulting a Du Pos baby that is DAT Neg?

[Barbarakym]

I recommend you reading the AABB guidelines pamphlet on Prenatal and Pregnancy and neonate testing, I am sorry I am at home and don't have the booklet here.This was as a 2005 publication.

According to that booklet, the ONLY patients required for testing are neonates born to Rh Negative mothers and THEN for the exclusive purpose of being able to give the mom's Rhogam should the baby type as Du positive (as weak D is still D from the perspective of donating cells to an Rh negative person- in blood donation and in protecting the mom with rhogam). This testing is done to protect the MOTHER.

In this same booklet talking about MOTHERS....The AABB says CLEARLY that you must have a policy for not calling a mom Rh positive who might actually be Rh negative. You must have a policy which protects against accidently calling an Rh neg mom Rh pos due to a fetal maternal hemmorage, which can present as Du positive. In another section it states that Du positive mothers are candidates for Rhogam because it is not easily determined if they are weak D or mosaic. And being Rh negative, Du positive is not a reason to withhold rhogam.

The booklaet is pretty cheap on AABB website and it also gives lots of information on titers and antibodies which affect the pregnancy and HDFN testing recommendations, etc. So I read and re-read this book while making my policy this year and the above is what we determined they were requiring and recommending which is why the policy is written the way it was.

The ONLY tricky thing for us was....if you don't normally do DU testing but you do on a neonate HOW do you handle that baby's records so as not to be confusing later when the baby came back as a patient? As a patient the neonate would be called Rh negative.....thus we decided to NOT report the baby's incubated typing, but rather to treat this baby as an unknown Rh as that is how we treat babies with positive coombs and the mother is required to get the rhogam. Other places might handle this differntly. Still I am very comfortable with our decision as for protecting the mom with rhogam the action is the same and that is why we did the Du in the first place.

Again, I recommend you get that AABB pamplet and make your own determination.

[lalamb]

~5 years ago we had a Rh "Pos" adult who was given Rh pos blood and developed and anti-D. Checking the pt's history , turned out he was a Du pos. So, we stoped testing/reporting Du status on adults.

If D = neg at IS, they are reported as Rh neg.

This, of course, has led to discrepancies w/some OB patients. Sent and explanitory letter to OB saying what had historically been done and why, and whats done now.

We only do Du testing on Rh neg babies of Rh IS neg mom's.

I am interested in the verbage of "Rh indeterminate" for the baby.

We currently call Rh IS neg, Du pos baby as Rh pos, to trigger Rhogam for the mom. But you are correct - don't want the "fake" Rh status of Pos to follow the baby into adulthood. Will have to look into that...

[LABLAD42]

So you are saying you want to find weak D patients? Why? Do you call then Positive and treat them as Positive?

I don't want to call them negative if the are just weakly positive

There is a difference between just weakly positive and Du positive.

If the patient gets tested at another hospital,I don't want him to say the he tested negative previously unless,it's just Du pos.

If you are interested .write me at lablad42@aol.com and I will fwd the pics I took of a case I had.

[jasonviau]

I'm so glad I happened across this thread this morning. Currently, we are only testing neonates for weak D. Just today, after reading through this thread, we had a woman present to Labor and Delivery. Her prenatal report from a reference lab stated that she was O Positive. We had history from a previous admission of her being O Negative, and the sample sent from L&D tested O Negative. The patient's nurse was quite flustered as to how there could be such a discrepancy. Turns out, the reference lab uses a Provue. I was able to explain to her the differences in sensitiviy between the manual tube and automated gel methods. I like the idea of 2+ or weaker on a machine being reported in tube. We're looking at automation; I'll have to remember to include that in my policy.

[khalidm3]

We perform weak D, for all our donors/patients including neonates. We write the Result Rh=Weak Positive If the AHG test is positive. We label our blood units as Positive and release Rh Negative blood for all such patients. We test all our babies by DVI+ Anti D and patients/Donors by DVI- Anti D. Will AABB or Joint Commission have Objection.? We adopted this policy to avoid Confrontation with patients/Donors/Physicians.

How to face Confrontation when a neonate cord blood group testing and transfusion order blood group testing if he/she is weak Rh. A risk lies in our policy, physician may not prescribe RhIG upon Weak Rh positive result considering it positive for a mom. Shall we write in our comments to prescribe RHIG what is best to to adopt????????? Shall we shift like urs as above.

Edited October 14, 2010 by khalidm3