Weak D in gel?

[bevydawn]

I have seen on other threads where people are performing weak D testing using IgG gel cards. Being a huge fan of gel I was wondering if someone could give me more information on how you do this. Is it as simple as it sounds? Another concern I have is how could I possibly vaildate this? Although we do many weak D tests on cord bloods and prenatals, we rarely ever see a positive result. It would take us forever to get 20! Any suggestions?

[Likewine99]

Make the 0.8% suspension of cells, add 25 uL of anti-D tube reagent to the tube, incubate 10 min and centrifuge. We put the word out to our sister hospital BB's for specimens and checked with the blood supplier and reference lab.

We only had 8 samples and it took forever but it was 100% correlation and worth it.

[David Saikin]

Make certain that your tube anti-D will detect DVI. 50uL of 0.8% cells/25uL anti-D, in IgG card. 37C for 15 minutes/10 minute spin. All my "classic" weak D pts come up 3+ with ABD cards. I have 2 documented DVI pts that I used for my validation.

[DAWNA1983]

I had a positive weak D in gel about a week ago. I confirmed it by tube method.

[PHYLLIS]

Hi David,

We do all of our types in gel. So, are we missing DVI patients? We do our retypes in tube. We only do retypes of there is no history.

[David Saikin]

Phyllis

The anti-D in the gel ABORh card does NOT detect DVI (on purpose). These pts are the ones who usually will develop anti-D (classically Weak D+ with anti-D). Not all tube testing anti-D's will detect the DVI so you have to read your package insert. Quotient Biodiagnositcs has a D Blend which can detect DVI at immediate spin. I have not played with it in gel. They also have 2 IgM anti-D's, but they do not detect DVI. If you do not collect blood donors you should be doing Weak D testing on your Rh negative cord specimens from Rh negative mothers.

I have a few other patients in the area who type as w+ with all anti-Ds that I have tried, whether it be in gel or tube/immediate spin or ahg phases . . . a few of them were OB pts - I told their doc that I knew they had D ag on their red cells but we were going to consider them as Rh=. Interestingly, they were 2+ macro with the rosette test.

Edited November 24, 2010 by David Saikin
added more on the topic

[Deny Morlino]

David,

We use the Albaclone D delta from Quotient when we have a cord blood result Rh negative in Gel. It is a direct method as you indicated. Our experience has been that the D delta rolls off stronger in tube than the same samples using an extended incubation protocol. My techs appreciate the time savings associated with the reagent, not to mention the reduced chances for error due to technique. Just food for thought.

[PHYLLIS]

Hi David,

After hashing this over, I guess my true question is we are missing weak D reactions in gel. Which means we report out all positive reactions in gel as Rh positive. That includes women of child bearing age who should receive Rh negative red cells if they are a weak D. I don't want to have two different procedures for certain age groups. What are your thoughts?

Thank you