Anti-D titers on OB patients

[caj1018]

We have an OB doc in our community that read that 1.7 % of Rh neg OB patients make Anti-D even when they get antenatal RhIg so he wants an automatic Anti-D titer on all patients that have an Anti-D detected when the patient is admitted for labor - even though they know the patient received RhIg and the screen was negative prior to the dose. This doc practices at a "sister" hospital and the Pathologist there have asked for info on how to handle this situation. All OB patients have a TS ordered when admitted for labor. This hospital uses gel technique. I suggested that if they identify an Anti-D they repeat the antibody screen using tube technique and if negative then not perform the titer. What do other labs do? Is this a situation that has arisen elsewhere? Any words of wisdom would be greatly appreciated. Thank you.

[Mary]

If you know that the patient received antenatal Rhogam, you can run an antibody screen with Rh Negative cells to screen only for other antibodies. 3 or 4 cells on Ortho Resolve Panel A are always indicated for this use. This may not solve your OB physician situation, but if you don't detect it, you don't have to titer it!

Also I think there is a technique to differentiate between rhogam and immune anti-D. See Technical Manual, page 548. Titering Rhogam seems like a waste of time and money.

Gel is more sensitive to detecting Rhogam.

Good luck.

[Seveets]

If you know that the patient received antenatal Rhogam, you can run an antibody screen with Rh Negative cells to screen only for other antibodies. 3 or 4 cells on Ortho Resolve Panel A are always indicated for this use.

Hi,

I'm wondering how many people use the quick 3-4 cells in the Ortho Panel A to rule the antibody as Anti-D?

To you do it just for Rhogam patients or what about elderly patients with a history of Anti-D?

Thanks

[GilTphoto]

We only do a titer of anti-D if it reacts stronger than 2+, or reacts in a phase other than IAT (IS or 37C). If the titer is less than 1:4 it's passive anti-D.

Gil

[John C. Staley]

We only do a titer of anti-D if it reacts stronger than 2+, or reacts in a phase other than IAT (IS or 37C). If the titer is less than 1:4 it's passive anti-D.

Gil

Gil that is a pretty strong statement. I would take issue with any of my techs making it if there is no evidence of a RhIG injection in the recent past.

:abduction

[Mabel Adams]

So, lets say you titrate all these OB samples. What is the doctor going to do with the info? Is he going to forego postnatal RhIG (heaven forbid)? Is he going to panic the mother that her baby will be sick? As long as the reactions are not strong and not detectable at some other phase than IAT, why not just see if the baby has a pos DAT? What are they going to do about it anyway, if it isn't detected until delivery? The point then will be to treat the baby based on if it is affected and how much. If they need to know for next pregnancy, then they should do a repeat Ab screen on the mom about 6 mo. post delivery.

You might need to do further studies in the A+ baby of an O neg mom that has a pos DAT. Even then, a titer won't really clinch the case for you. The eluate will be of more use. I believe RhIG can sometimes cause a pos DAT in the baby, although probably more likely right after it is given than 3 mo. later. Of course, we must always err on the side of giving RhIG when it is not needed, rather than withholding it when it is.

[johna]

Page 548 of the Technical Manual gives a very inexact method of postulating whether the anti-D is active or passive and how often are any of us encountering an IgM-only anti-D to indicate active immunization. If the antibody reacts at room temp and in the Coombs phase I would seriously doubt the chances of 2ME or DTT solving the problem.

We deal almost exclusively with a prenatal population and if the intial screen is positive by solid-phase and the antibody is identified as anti-D a tube screen that gives a reaction of less than a good 1+ is resulted with a "too weak to titer" comment. We still have docs calling up asking for an exact titer.

[GilTphoto]

John,

Of course we back up a report of passive anti-D by investigating whether the patient actually got ante-partum RhIG at another facility, if not in our records.

As far as the baby's results, even if the baby's DAT is positive and you elute anti-D, the doctor won't care as long as the bilirubin stays low.

We had a mother with an anti-D with a titer of 256, and an anti-C with a titer of 128. Both antibodies were eluted from the baby's cells. The baby's first total bilirubin was 3.2. The next day 6.5, the day after 14.9. Then it started going down and the baby was discharged.

Gil

[csjuarez]

We use the D- "mini panel" when the D+ cells of the antibody screen are positive and we confirm that the patient has received RhIg. We do not do this "mini panel" for anti-D in other patients.

Titering any antibody at the time of delivery or post-partum seems to be a colossal waste of time, energy, and resources. The point of these titers is to help determine if the antibody is currently being stimulated and may effect the baby. And I would consider a request to titer anti-D after we know RhIg has been administered as preposterous (and I believe my Medical Director would back me up 100% on that!). As someone has already said, post-partum the focus switches to the baby, and clinical decisions will be made relative to the baby's condition, not the mother's antibodies.

[johna]

John,

Of course we back up a report of passive anti-D by investigating whether the patient actually got ante-partum RhIG at another facility, if not in our records.

As far as the baby's results, even if the baby's DAT is positive and you elute anti-D, the doctor won't care as long as the bilirubin stays low.

We had a mother with an anti-D with a titer of 256, and an anti-C with a titer of 128. Both antibodies were eluted from the baby's cells. The baby's first total bilirubin was 3.2. The next day 6.5, the day after 14.9. Then it started going down and the baby was discharged.

Gil

Thanks for the response Gil. Unfortunately as a reference lab we are privy to zero patient history information. If we called every client who sent us a weak anti-D we'd have to hire an FTE just for phone calls.

[Oldtimer]

CSJuarez has this response perfect. Titering at delivery tells you nothing.