We do not routinely do weak D testing on prenatal samples. I am interested in how you explain to the doctor when the patient has a positive fetal screen rosette test due to the fact that she is actually weak D positive. Do you give multiple vials of Rh immune globulin if the KB stain indicates that they are needed?

You should not report a positive fetal screen on these patients since the test is inappropriate. Your policy/procedure should include that when a macroscopic result occurs you perform a weak D test and a specific test for fetal hgb, either by flow cytometry or a Kleihauer-Betke stain. If the K-B indicated more than one vial of RhIg I provide the amount indicated plus one vial. Just as an aside to the K-B, if you have pt with a persistance of fetal hbg (for whatever reason) it is prudent to perform a baseline K-B early in the pregnancy so that if a K-B is done later you can account for the % of maternal cells that test positive.

How would you know which patients have persistent fetal Hgb? Or do you mean known thalassemias etc.? The only ones I have ever seen gave no reason to suspect persistent Hgb F until we did the KB.

Mostly thall minors - hopefully the OB doc will know ahead of time . . .

Mostly thall minors - hopefully the OB doc will know ahead of time . . .

Ah...but will he tell US ahead of time? That's always my problem. I haven't yet figured out how to convince the docs that we can be more effective if they give us a little information about their patients. Has anybody out there found a good way to achieve that?

You should not report a positive fetal screen on these patients since the test is inappropriate. Your policy/procedure should include that when a macroscopic result occurs you perform a weak D test and a specific test for fetal hgb, either by flow cytometry or a Kleihauer-Betke stain. If the K-B indicated more than one vial of RhIg I provide the amount indicated plus one vial. Just as an aside to the K-B, if you have pt with a persistance of fetal hbg (for whatever reason) it is prudent to perform a baseline K-B early in the pregnancy so that if a K-B is done later you can account for the % of maternal cells that test positive.

page 631, 16 ed Technical Manual states:

mother's positive for weak D's are not candidates for RhIG

We are currently in the dilema with being required by corporate desision, to no longer perform weak D testing (except for infants) starting with our new computer system

We currently perform weak D on everyone, and report as Rh positive if weak D pos. Fetal Screen=Not indicated, RhIG=not indicated

But the Rh Chapter says, weak D testing is not necessary in recipients.

So there is the conflict!

As a blood recipient we can call her Rh Negative, but as a pregnant mother, she should be considered Rh Positive for the purposes of RhIG.

They said we can report the weak D test, but can't call the patient Rh Positive, since the computer doesn't consider the weak D in the determination of the Rh.

Can't even override it

I guess I'm old school and don't want to let go of the weak D test. We have had a serious shortage of Rh negative blood, so would prefer to save it for true Rh negatives.

Let it go . . . and besides, the Technical Manual does not know the reason the pt is Weak D+. If they are missing some of the mosaic they can become sensitized.

Let it go . . . and besides, the Technical Manual does not know the reason the pt is Weak D+. If they are missing some of the mosaic they can become sensitized.

Absolutely! Weak D is important, as you said Dave: "If they are missing some of the mosaic they can become sensitized."

It would be dangerous to consider a recipient who is weak D as positive while claiming that s/he is not a true D negative. Even more so, if the recipient is a pregnant lady: weak D must be considered D negative for the mom and watch out for HDNF.

Donors are considered to be positive if weak D. While ANY recipient including a lady in gestation is considered D negative if weak D. Please administer RhIg.

To GilTphoto:

Question: Would you give a weak D recipient blood from a weak D donor?

Please say no.

And a weak D recipient cannot, must not and should not recieve blood from a weak D donor. Its like giving D pos to D neg... surprises may happen....

Actually Liz, I hate to say this, but we would give D Positive blood to a WeaK D Types 1, 2 and 3 recipient, but not to a Partial D recipient, or a Weak D with a Type "below" 3, but then we also type any such patient with a whole battery of monoclonal anti-D reagents from Alba Bioscience (when they are available - ahem, we are having trouble sourcing these at the moment).

Unless you are the donor center doing the D testing how would you ever know if a D positive unit is weak D or not?

There was a time when a wD+ patient was simply considered D+ for transfusion purposes. I imagine in many places with out Malcolm's resources they still are.

:eyepoppin

You have it John - we end users will never know if the Rh+ unit is from a WeakD+ donor.

Well, actually, John and David, does it matter if the DONOR is a Weak D or a Partial D or a "normal" D, if the blood is labelled as D Positive? Such blood should ony be given to a D Positive recipient (or a proven Weak D Type 1, 2 or 3), and they are not going to make anti-D (under normal circumstances). If anything, they could may something like an anti-BARC (but would you ever know), and, if they did, it would make their fortune!!!!!

It's the D group of the recipient that counts.

Malcolm - I would hazard that most of us here do not have access to the Alba (Quotient in the US) D typing panel. Actually, most of probably do not perform Weak D testing at all except on cord bloods (personal opinion). The only time I use that panel is when I have a weak D typing in gel and subsequent tube/Weak D testing is also very weak.

Actually Liz, I hate to say this, but we would give D Positive blood to a WeaK D Types 1, 2 and 3 recipient, but not to a Partial D recipient, or a Weak D with a Type "below" 3, but then we also type any such patient with a whole battery of monoclonal anti-D reagents from Alba Bioscience (when they are available - ahem, we are having trouble sourcing these at the moment).

Ofcourse I agree with that Malcolm, but how can the non reference labs know the difference, we cannot with the routine testing. I did work in a hospital in the US in '97 where they gave D+ to weak D recipients, the logic behind it was that weak D is rare and mosaic (partial) weak D is even rarer, so instead of wasting D- they gave D+. I do not agree.

So it is always: the weak D patient is documented as Negative and the weak D donor is documented as Positive. UNLESS the donor later becomes a patient and the patient a donor :cool: Theoretically you are right but on the ground we must make do with what reagents we have. I am right !!

I would like to share a story: We had an OB patient that was new to our hospital and we typed her as D pos (Gel System 4+). She insisted that she always received RhIG with her previous births. So I called the hospital blood bank to inquire about her type. They had her as O neg, weak D pos. So naturally I done the testing in the tube and she was weak D. The doctor dosed her with RhIG because of the mosiac or missing parts of the D antigen. So are we missing these patients that are true weak D and have the potential to make an antibody to the missing parts. I would like your thoughts. Thank you.

I assume that the gel you are using does not have DVI+.

Ofcourse I agree with that Malcolm, but how can the non reference labs know the difference, we cannot with the routine testing.

Fair comment Liz. I keep forgetting that I'm working in an "Ivory Tower"!!!!!!