Hello all,

I was asked by another smaller lab if we can do an antibody screen on a cord blood. 

• Me: it would be more appropriate to do an antibody screen on the mother. 
• Them: Mother has Anti-D due to RhIG. A Neonatologist from a larger city is recommending they do the antibody screen on the baby.
• Me: If they want an antibody screen we can do it on a peripheral draw from the baby, but it seems more appropriate to do the DAT on the cord.
• Them: The Dr. was asked if they wanted the DAT and they sad no, only the antibody screen and specifically on the baby. Patient is discharged we won't get a peripheral draw.
• Me:  I can do a DAT and if positive do an elution on the cord blood.

Why would a Neonatologist be insisting on an antibody screen on a baby knowing the mother was given RHIG?

I haven't considered doing an antibody screen on a cord blood because of the Wharton's jelly.  Is there any other reason we would not use Cord?

Also in a separate situation I have been told to do an antibody titer on a RHIG patient by I suspect the same Neonatologist.  What information would be useful from a titer with RHIG?

Thanks in advance for sharing your wisdom

There is no reason why you shouldn't do an eluate on cord blood (the washing would also wash away any Wharton's jelly, so there would be no interference).

The only information you would get from a titre on the mother's plasma would be to tell if the anti-D really is from the immunoglobulin jab, or whether it is an immune anti-D.

I think both are usually a waste of time!

Why do I get the distinct feeling that someone is not giving you the full picture on this one....???

6 hours ago, Malcolm Needs said:

There is no reason why you shouldn't do an eluate on cord blood (the washing would also wash away any Wharton's jelly, so there would be no interference).

The only information you would get from a titre on the mother's plasma would be to tell if the anti-D really is from the immunoglobulin jab, or whether it is an immune anti-D.

I think both are usually a waste of time!

Thank you Malcolm.  Can you explain how the titer is able to differentiate immune from a "jab"?  I was with the understanding they are both variable in strength depending on the patient. 

7 minutes ago, tkakin said:

Thank you Malcolm.  Can you explain how the titer is able to differentiate immune from a "jab"?  I was with the understanding they are both variable in strength depending on the patient. 

If the titre is weak, it could be either, but if the titre is high, then it must be immune.

studies have shown that, even when repeated large doses of IM anti-D immunoglobulin are given, the titre still remains low.

That having been said, even if the titre is high, this will affect the next pregnancy, rather than the pregnancy just gone, unless the baby itself is showing signs of HDN.  If the baby is affected by HDN, then the titre result will not affect the way the baby is treated; the condition of the baby will govern this.