If you have an D=, Weak D+ neonate, do you call them Rh+ or Rh=?

Well, you cannot call the baby Weak D+, as there is no such antibody as Anti-Weak-D, but to answer your intended question, it depends on whether or not the baby's red cells are DAT Positive or not, and also on what epitopes your anti-D are designed to detect.  It could be that the baby is a Partial D.

34 minutes ago, Malcolm Needs said:

Well, you cannot call the baby Weak D+, as there is no such antibody as Anti-Weak-D, but to answer your intended question, it depends on whether or not the baby's red cells are DAT Positive or not, and also on what epitopes your anti-D are designed to detect.  It could be that the baby is a Partial D.

But the final interpretation of Rh would be positive or negative?????

8 minutes ago, pbaker said:

But the final interpretation of Rh would be positive or negative?????

Until there is a definitive answer, it MUST be D Negative, even though the chances are that, at that stage of life, the baby's immune system would not produce an anti-D if D Positive blood was transfused, BUT it could well be that the baby's immune system could be sensitised to the D antigen.  ALWAYS ERR ON THE SAFE SIDE.

BCSH guideline for the use of anti-D immunoglobulin for the prevention of haemolytic disease of the fetus and newborn states 'Anomalous or indeterminate cord Rh D groups should be treated as D positive until confirmatory testing is completed.'

For neonate transfusions see Malcolm's answer.

 

For the immediate time frame, with the mother in mind, consider the baby as D+ and provide RhIG.   On the other hand, with concerns for the baby, D= is how I would treat the baby. 

Hard to know what to do.  Most weak D patients will not make antibodies to D epitopes.  Most antibodies to D epitopes will not cause serious hemolysis.  But we don't have enough clinical data to predict which patients will make antibodies and which antibodies will be dangerous after transfusion or cause hemolytic disease of the newborn.  Hence we usually treat these patients as Rh positive for purposes of administering Rh immune globulin to the mother, and as Rh negative for transfusion purposes.  Not a major public health problem, but challenging.

Interestingly, automated gel technologies, and manual versions of these, often type patients as strongly Rh (D) positive when tube testing shows weaker reactions (2+ or less has semi-arbitrarily been chosen).  So we will soon be finding whether these patients can make anti-D antibodies and whether these antibodies are clinically significant.  My best guess is mostly not an issue.  It does solve the Rh immune globulin question, since the baby is Rh positive and one administers RhIgG to Rh negative mothers.

18 hours ago, Malcolm Needs said:

Until there is a definitive answer, it MUST be D Negative, even though the chances are that, at that stage of life, the baby's immune system would not produce an anti-D if D Positive blood was transfused, BUT it could well be that the baby's immune system could be sensitised to the D antigen.  ALWAYS ERR ON THE SAFE SIDE.

I agree with this if we are transfusing.  We would use O= anyway.  I'm talking about just the basic blood type of the baby.

1 hour ago, pbaker said:

I agree with this if we are transfusing.  We would use O= anyway.  I'm talking about just the basic blood type of the baby.

The ONLY way this can be determined accurately is by molecular, rather than serological techniques.  The reason I say this is because, although we tend to think in terms of foetal to maternal bleeds (foetal blood into mum's circulation), there is always the chance that the bleed can be maternal to foetus, thus meaning that serological testing can be unreliable at this stage of life.

We would label the child rh+. The only problem this might cause is if the child returns to our hospital as an adult (we do not treat pediatrics in my facility) and required blood. The initial blood type might seem like a discrepancy since, conceivably, they would initially type rh negative but their historical record would say positive. Of course, we would simply verify this by looking at the previous testing results stored in our LIS.

I have frequently seen Rh discrepancies like this with hospital hoppers.  If we have (or can get) last hospital history one phone call resolves issue (plus weak D test). However We have had problems when the patient is adamant they are Rh pos (or neg) and we report the other. This has caused long delays for patients to get or accept the explanations and give consent (or re-consent) to be transfused. The added tech time for these situations can be frustrating on occasion. 

We report the baby as Rh negative, weak D test positive (if DAT is negative), mother is a candidate for RhIG.

On 11/4/2022 at 7:22 AM, AMcCord said:

We report the baby as Rh negative, weak D test positive (if DAT is negative), mother is a candidate for RhIG.

Can your computer system do that?  Ours cannot.

On 11/7/2022 at 3:06 PM, pbaker said:

Can your computer system do that?  Ours cannot.

Yes, we built the weak D test as a separate test. The results of that test are not directly linked to the patient blood type. On cord bloods we report that result more as an interpretive comment to help OB nursing staff understand why mom is a candidate for RhIG AND we also tell them with another 'test' that RhIG is recommended if baby's weak D test is positive. Just to make sure we are all on the same page.

This is Shrodingers D - Treat the mum as if the baby is D+, treat the baby as if they are D-