An example of Anti-G Separation/Differentiation - Any thoughts? Thank you!

Anti-C.-D.-G separation.HEIC

In the UK, we would test serum/plasma samples from pregnant patients to see if there was an anti-C + Anti-G, or an anti-G on its own, but if the tests showed an anti-D+C, we didn't go any further to see if there was an anti-G there as well.  I mean, what for?  What difference does it make?

I attach a PowerPoint lecture on the subject I wrote some years ago, but I think it is still pertinent.

The G Antigen and Anti G.pptx

Happy Friday everyone! 

First off, Thank you Malcolm 😊 for that excellent PPT lecture! 👌 With your permission, I'd love to share it with my students; it's exactly the kind of content that helps bring these complex concepts to life (and mildly melt brains in the best way possible).

Speaking of melted brains… let's talk Anti-G differentiation, shall we? While I agree that differentiation isn’t necessary for transfusion purposes because in cases where anti-G is suspected, the recommendation is the same (D and C antigen-negative PRBCs); in the US Reference Lab world, it's a whole different dance. Differentiating anti-D + anti-C from anti-G is essential in alloimmunized patients with anti-D + anti-C for Rh Immune Globulin (RhIg) prophylaxis administration indication. Medical teams want to know if a patient is a candidate for RhIG, and if it's still indicated, especially to avoid future medical and legal complications. And so begins the beautiful (read: painstaking) double adsorption and elution process. 😫

 

The presence/development of a real anti-D indicates the patient does not require RhIg administration, whereas the presence of anti-G indicates the need for RhIg prophylaxis. That way, RhIG is avoided in patients with a real anti-D (although clinical correlation is recommended to guide every decision).

In this case, we saw what looked/reacted like anti-D and anti-C (1). Adsorption with R2R2 cells showed anti-C in the adsorbed serum (2) and anti-D and/or G in the adsorbing R2R2 cell eluate (3). Usually, we would stop and call anti-C and anti-D, if we have no reactions on C Ag Pos cells, but since suspected anti-G was in the mix, we routinely differentiate/separate it. The anti-D was confirmed in (4) by adsorbing the eluate containing the suspected (anti-D + anti-G) with an r'r unit. So far, so good. However, when we tried to separate the anti-G by elution of the adsorbing r′r cells, expecting a reaction on D and C antigen-positive cells (5), we got a negative result (Cue dramatic music).

I know, I know...at this point you’re probably wondering if we’re still in the Blood Bank or if we’ve accidentally wandered into theoretical physics. Trust me, my brain also wobbles when explaining G differentiation. It's the kind of thing that makes you rethink your career choices... for about 5 minutes... and then roll up your sleeves and start prepping another adsorption. 😅

A couple of housekeeping: We ficin treat our adsorbing cells, and sometimes use PEG in adsorption for efficiency. After briefly considering a career in something less chaotic, we retraced our steps. No PEG this time, 60-minute incubation, followed up with a DAT after each adsorption to check for antibody coating... and voilà: finally got the positive reaction we were looking for. The patient has anti-D, anti-C, and anti-G.

I can only think of a possible weak DAT strength pending elution, or PEG interference when used in adsorption. As always, this is Blood Bank, we know a million things can go wrong, and often do. But in the end, science (and a lot of perseverance) wins. 

Thanks again to everyone for your input, patience, your brains, and your sense of humor. And again, Malcolm, thanks for your lecture, teaching, dedication and inspiration!

I wish everyone a calm weekend. May your panels be clear, your DATs negative, and your eluates informative. 😉

 

I almost forgot, here you go!

Image 1 .jfif Image 2 .jfif

Thank you for your exceptionally kind words DLabGirl, and by all means use the lecture as you wish.  The same goes for anyone else who might want to use it, with the proviso that you a) realise that it is a bit "long in the tooth", and b) I did mean that we, in the UK, would still look to ensure that there really is an anti-D present, before we do not recommend giving anti-D immunoglobulin.