Has anyone validated weak D testing using the MTS anti-IgG cards?

No, but I think you will find that patients that were 'weak D' in tubes will be Rh pos in the ABD/reverse cards. In a little more than a year we have found at least half a dozen patients that were Rh neg in tube testing that are Rh pos in gel. These were confirmed 'weak D' after the gel cards were Rh pos. ( we routinely do 'weak D' only for childbearing aged women and cord blood.)

We do weak D testing in an IgG MTS gel card. We only do weak D testing for Rh neg moms and cord bloods.

About once a quarter or so we get someone who historically typed Rh neg in tube that we now get as Rh pos with gel cards.

we also only perform weak D's on prenatals & cords. The dilemma I am facing is how to find weak D samples, unless we test all of our patient population who is Rh negative.

Hi everyone,

Weak D testing on prenatals and Rh negative females of child bearing age is not required. Weak D testing is only required on red cells of donors and infants when determining if mother is RhIG candidate. The current Technical Manual has a nice little explanation about D typing of donors and patients and why D typing on all patients is not required.

JB

Hi everyone,

Weak D testing on prenatals and Rh negative females of child bearing age is not required. Weak D testing is only required on red cells of donors and infants when determining if mother is RhIG candidate. The current Technical Manual has a nice little explanation about D typing of donors and patients and why D typing on all patients is not required.

JB

You are correct, and that is our policy. However I end up on the phone at least 3 times a week explaining to physicians why we typed the mother as "negative" but when she delivered, the hospital (who still performs Weak D testing) typed her as Rh positive. And they do not understand when I say "both results are correct".

Since the D clone in gel is different than the D clones in the tube reagents, you will get variability of reactions. One of the most significant differences is partial D VI, which is negative in gel and immediate spin tube, and positive weak D with Ortho and Immucor tube reagents. Patients with partial D VI could make anti-D if transfused with D positive blood.

At our facilities, when we switched to gel at 3 of our 4 sites, we dropped weak D testing. We found that some patients would test as D negative immediate spin, then D positive in gel the next day for the RhIg workup.

Our solution: We test all immediate spin D negative patients either in gel or IAT. We use the gel result or the negative weak D as our test of record. If the patient tests as weak D positive, or has a history of weak D positive, we test them in gel and use the gel result as our test of record. We never accept weak D positive as a result. The gel D result or weak D negative result goes into their BB record and we do not need to do additional testing once recorded.

For infants, we run tube testing IAT on all gel D negative cords, because we do not want to miss the partial D's. If weak D is positve, then mom is a RhIg candidate, KB stain instead of fetal screen (Yuk). However, the baby would be considered D negative is transfusion was required.

D testing can be a pain, but our protocol seems to work for us.