Anti-G investigation

[Rhona24]

Does anyone have a validated method for the investigation of Anti-G?

[Malcolm Needs ☆]

One way is to use the extremely rare r"Gr red cells, but most people do not have access to such rarities.

The other is to split the plasma into two aliquots.

The first is adsorbed with Ro red cells, which will have the effect of adsorbing out both anti-D and anti-G, but leaving any anti-C. After this adsorption, test the adsorbed plasma against r'r red cells. If there is an anti-C present (as there often is with an anti-G), then the r'r red cells will react.

The second aliquot is adsorbed with r'r red cells, which will have the effect of adsorbing out anti-C and anti-G, but leaving any anti-D. After the adsorption, test the adsorbed plasma against Ro red cells. If there is an anti-D present (as there sometimes, but rarely is, with an anti-G), then the Ro red cells will react.

If, originally, there was only an anti-G present, the r'r red cells will not react with the plasma adsorbed with the Ro red cells, and the Ro red cells will not react with the plasma adsorbed with the r'r red cells.

If, originally, there was anti-C and anti-G present, the r'r red cells will react with the plasma adsorbed with the Ro red cells, but the Ro red cells will not react with the plasma adsorbed with the r'r red cells.

If, originally, there was anti-D and anti-G present, the r'r red cells will not react with the plasma adsorbed with the Ro red cells, but the Ro red cells will react with the plasma adsorbed with the r'r red cells.

Finally, if the r'r red cells react with the plasma adsorbed with the Ro red cells, and the Ro red cells react with the plasma adsorbed with the r'r red cells, then the plasma originally contained anti-D+C, +/- anti-G.

Hope that helps.

[Joanne P. Scannell]

I think the big question is: Do you really need to do this in your lab?

The concern is mainly about Rh-immune globulin candidacy. (It's easy enough to find D-neg,C-neg RBCs for transfusion, so pretransfusion candidates are not an issue here.)

How often will a pregnant woman present in your lab with "Anti-D,-C" ... possible ONLY Anti-G or a combo of Anti-D,-G?

If that number is low/rare, is it worth it to find all these cells ... and to actually find enough to accomplish these elutions (and don't forget controls and competency!) for those few times? Or, is it better to send the sample to a reference lab? OR is it better to just make a policy to classify patients producing Anti-D,-C as candidates and give them the Rh-Ig and not be concerned if it's ONLY Anti-G? (Which in itself, I hear is unlikely.)

[Rhona24]

Thanks for your replies. We need to do Anti-G investigation as the BCSH guidelines recommend it for pregnant women with apparent antiC+D specificity. At present we use papainised r'r and R2R2 cells to adsorb the plasma and perform elutions on the adsorption cells.

Malcolm- do you use papainised cells for your adsorptions and do you use any controls?

[carolyn swickard]

We once had an anti-G investigation too - so just anothr question. A reference lab I contacted said a possible way to judge whether the mother was still a candidate for RhIg was to titer the "anti-C" separately from the "anti-D". As long as the titer for the "anti-C" stayed higher than the titer for the "anti-D", it was most likely to be Anti-G and the pt was still a condidate for RhIg. Once the titer for "anti-D" passed the titer for "anti-C", there was probably a real anti-D involved and the pt would no longer be a candidate for RhIg. Any thoughts on that method - anyone else ever hear of doing it that way?

[clmergen]

I did have an apparent Anti-D,C on a pregnant woman. I sent it to the reference lab after confirming they had the G negative cells. I can't exactly remember the outcome, but I think she had an Anti-D and Anti-C.

[Malcolm Needs ☆]

I think the big question is: Do you really need to do this in your lab?

The concern is mainly about Rh-immune globulin candidacy. (It's easy enough to find D-neg,C-neg RBCs for transfusion, so pretransfusion candidates are not an issue here.)

How often will a pregnant woman present in your lab with "Anti-D,-C" ... possible ONLY Anti-G or a combo of Anti-D,-G?

If that number is low/rare, is it worth it to find all these cells ... and to actually find enough to accomplish these elutions (and don't forget controls and competency!) for those few times? Or, is it better to send the sample to a reference lab? OR is it better to just make a policy to classify patients producing Anti-D,-C as candidates and give them the Rh-Ig and not be concerned if it's ONLY Anti-G? (Which in itself, I hear is unlikely.)

I agree that this kind of thing is probably best done by a Reference Laboratory, or, at least, it is best confirmed by a Reference Laboratory (I hate to try to stop people trying to perform tests at their own hospital if they so wish - how else are they going to learn?, but, as you say, there is the question of comptency if the test is only performed once in a blue moon, although they are adsorptions, rather than elutions).

I do think though, for pregnant ladies, or, indeed, any female of child-bearing potential (horrible "politically correct" phraseology) that it is important to distinguish anti-D+C from anti-C+G (I agree that anti-D+G, without anti-C, and monospecific anti-G are both very rare), because, whereas anti-G, in rare cases, can cause nasty HDN, it tends not to cause HDF, whereas anti-D will cause severe HDN and HDF. Therefore, as you say, such ladies should be offered anti-D immunoglobulin, BUT, I'm not sure that I would offer anti-D immunoglobulin to all of them that look as though they have anti-D+C, just in case. Although anti-D immunoglobulin has not been implicated in many cases of "transfusion-transmitted infection", and has only rarely caused any problems with patients that have anti-IgA, it is the viruses that we don't know about that worries me.

[Malcolm Needs ☆]

Thanks for your replies. We need to do Anti-G investigation as the BCSH guidelines recommend it for pregnant women with apparent antiC+D specificity. At present we use papainised r'r and R2R2 cells to adsorb the plasma and perform elutions on the adsorption cells.

Malcolm- do you use papainised cells for your adsorptions and do you use any controls?

The BCSH Guidelines do, indeed, recommend that anti-G or anti-C+G be distinguished from apparent anti-D+C, but they also point out that, in such cases, the anti-C titre is disproportionately high, when compared to the apparent anti-D.

This is not a 100% rule, as a few years ago we almost got our fingers burnt with a case where the apparent anti-C+D was so strong that both gave 5+ reactions and the anti-D level was well into the 20IU/mL zone, but the dad turned out to be r'r (as did the baby), and it was only after an awful lot of serology (and red faces) that we found that the antibodies present were actually very, very high titre anti-C+G.

Yes, we do use papain-treated red cells for the adsorptions, but untreated red cells for testing the adsorbed plasma by IAT afterwards.

We don't use controls any more. We used to, but they made the tests almost impossibly complicated, and finding samples of plasma that contained anti-G (very rare), anti-C+G, anti-D+G (very, very rare) and anti-D+C for the controls proved extremely difficult.

[Malcolm Needs ☆]

We once had an anti-G investigation too - so just anothr question. A reference lab I contacted said a possible way to judge whether the mother was still a candidate for RhIg was to titer the "anti-C" separately from the "anti-D". As long as the titer for the "anti-C" stayed higher than the titer for the "anti-D", it was most likely to be Anti-G and the pt was still a condidate for RhIg. Once the titer for "anti-D" passed the titer for "anti-C", there was probably a real anti-D involved and the pt would no longer be a candidate for RhIg. Any thoughts on that method - anyone else ever hear of doing it that way?

It is a "possible" way of distinguishing between anti-D+C and anti-C+G or anti-G, but see my comments above about getting our fingers burnt!

[lacs]

If, originally, there was only an anti-G present, the r'r red cells will not react with the plasma adsorbed with the Ro red cells, and the Ro red cells will not react with the plasma adsorbed with the r'r red cells.

Malcom,

Maybe I am over-reading your post or I am too sleepy to understand (since it's midnight now:), I am a bit confused about your paragraph above. I learned that G is present on most C+ and some D+ red cells, so your adsorbed plasma from Ro adsorption, if contains anti-G SHOULD react with r'r (dCe/dce) red cells AND plasma adsorbed w/r'r red cells (if has anti-G) would react w/Ro (Dce/Dce) red cells, correct? Maybe it's the terms that confused me. When you say plasma adsorbed with etc, did you mean what's left behind (vs what's pulled out)????

[lacs]

If, originally, there was only an anti-G present, the r'r red cells will not react with the plasma adsorbed with the Ro red cells, and the Ro red cells will not react with the plasma adsorbed with the r'r red cells.

Malcom,

Maybe I am over-reading your post or I am too sleepy to understand (since it's midnight now:), I am a bit confused about your paragraph above. I learned that G is present on most C+ and some D+ red cells, so your adsorbed plasma from Ro adsorption, if contains anti-G SHOULD react with r'r (dCe/dce) red cells AND plasma adsorbed w/r'r red cells (if has anti-G) would react w/Ro (Dce/Dce) red cells, correct? Maybe it's the terms that confused me. When you say plasma adsorbed with etc, did you mean what's left behind (vs what's pulled out)????

Never mind, I read it again and I got it.....................