B(A) pehnotype

[jamato]

We recently had a group B donor unit from ARC type as AB with our monoclonal anti-A. It appears to be the B(A) phenotype. I read in the Tech Manual how to resolve the discrepancy but I want to make sure it is ok to place the unit on the B shelf. The tech manual was vague about it.

[pbaker]

I would send it back to the blood center and let them deal with the discrepancy.

[PAWHITTECAR]

Our policy is to send it back!! In my many moons in blood bank I have had 2 instances where a unit did not type as expected. The 1st was labelled O and types as a VERY weak A come to find out it was a subgroup. It might not have been caught but working at a pediatric facility we looked at all of our forward groups under the scope (not units) so were used to looking for very week reactions. The second was labelled A Neg and we typed it as A Pos, After we returned it we received several calls back and forth because when they retested it they got negative again. We ended up testing it against 5 different manufacturers antisera and 2 out of the 5 were positive.

[Malcolm Needs ☆]

I would send it back too. It's their job to sort these things out AND, more to the point, if you gave it to a group A recipient, and they had a reaction, who would end up in court; you or them? If they got it wrong, it should be them, but, as I understand it, in the USA, it would be you because you "couldn't have tested it properly upon receipt". In the UK it would be the fault of the NHSBT - no argument.

[Dr. Pepper]

I agree completely - it's their problem, not yours. Send it back. Nothing wrong with having your own criteria for rejection such as ambiguous typing result, ? bloodstain on the label, etc.

[Emwilson7]

Hands down send it back, they need to resolve the discrepancy at the donor center.

Edited May 20, 2013 by Emwilson7

[jamato]

Thank you everyone for your quick responses. The unit was destroyed and credited by ARC.

[carmik]

We recently had a group B donor unit from ARC type as AB with our monoclonal anti-A. It appears to be the B(A) phenotype. I read in the Tech Manual how to resolve the discrepancy but I want to make sure it is ok to place the unit on the B shelf. The tech manual was vague about it.

Very interesting we received a B-positive leukoreduced RBC unit from ARC that retyped as an AB positive using BioRad reagents just this week. The A typing was 1+ with Anti-A reagents and we back typed the "plasma" from the segments and it confirmed the backgroup as AB. We had never seen this before. We sent it back to the ARC with credit but have not received any follow up.

[Malcolm Needs ☆]

This thread is frightening the life out of me!!!!!!!!!!!!!!!!!!!!

[goodchild]

Would a B(A) donor unit transfused to a B patient cause any sort of reaction? Has anyone read or heard anything about this? I'm curious.

[jamato]

That's what i'm trying to find out. ARC said the donor had 16 previous donations.

[Malcolm Needs ☆]

Would a B(A) donor unit transfused to a B patient cause any sort of reaction? Has anyone read or heard anything about this? I'm curious.

Unless the recipient has a very high anti-A titre, with lots of IgG anti-A, probably not (note the word "probably"), but I wouldn't like to be the one to make the decision.

I do know that Martin Ollson has shown that, when his group A cells that have been turned into "group O" cells, after treatment with "A-ase", they do not cause a transfusion reaction in group O recipients, but they DO cause a rise in anti-A titre. He said this at a BBTS ASM a few years ago now.

[Malcolm Needs ☆]

A thought has just struck me, and this thought also applies (but to a lesser extent) to the thread started by Rhfan. I suppose that you are actually detecting an A antigen, and not detecting a FORS1 antigen? Presumably, you are using a monoclonal anti-A, which would make this thought totally redundant, but I just wondered.

[Mabel Adams]

I'll bite. What's a FORS1 antigen?

[Malcolm Needs ☆]

FORS1 is the only antigen in the 31st Blood Group System, FORS. In 1987, three English families were shown to have members whose red cells were strongly agglutinated by the extract from the ova of the snail Helix pomatia, but not by Dolichos biflorus. The phenotype was called Apae. My friend and colleague, Bob Stamps has been following at least one member of these families for many years (a donor) and, evenutally, got the Swedish group interested. It was found that, what the family were expressing on their red cells was, in fact, the Forssman antigen, and was genetically seperate from the ABO locus.

Alpha3GalNAc, when attached to the H carbohydrate confers the A antigen, but alpha3GalNAc attached to the P carbohydrate confers the FORS1 antigen. Some polyclonal, but not monoclonal, anti-A reagents cross-react with the FORS1 antigen, which is why I had the sudden thought, but I doubt very much if my sudden thought has any milage whatsoever, as so few people use polyclonal anti-A these days.

[jamato]

That is very interesting. We are using a monoclonal reagent with the clone MH04.

[Malcolm Needs ☆]

Thanks jamato.

That confirms that it cannot be FORS1.

I'll have to have another think!!!!!!!

[Mabel Adams]

Who dreams up the idea of making extracts from snail eggs to try testing on human red blood cells?!?

[Malcolm Needs ☆]

Who dreams up the idea of making extracts from snail eggs to try testing on human red blood cells?!?

Prokop O, Uhlenbruck G, Kohler W. A new source of antibody-like substances having anti-blood group specificity: discussion on the specificity of Helix agglutinins. Vox Sang 1968; 14: 321-333.

Boyd WC, Brown R. A specific agglutinin in the snail Otala (Helix) lactea. Nature 1965; 208: 593-594.

Hammarstrom S, Kabat EA. Studies on specificity and binding properties of the blood group A reactive hemagglutinin from Helix pomatia. Biochemistry 1971; 10: 1684-1692.

to name a few. It was all to do with getting sufficient high titre reagents to use on the primitive automated grouping machines of the time.

[galvania]

Perhaps this is a silly question but why can't the units in question just be AweakB (for example AxB) rather than B(A)? Some of these really weak A antigens can be very difficult to pick up

[Malcolm Needs ☆]

I agree Anna.

[Malcolm Needs ☆]

I'll bite. What's a FORS1 antigen?

The definitive paper on this subject has just been published Mabel (and any other interested parties, come to that). It is:

Svensson L, Hult AK, Stamps R, Angstrom J, Teneberg S, Storry JR, Jorgensen R, Rydberg L, Henry SM, Olsson ML. Forssman experssion on human erythrocytes: biochemical and genetic evidence of a new histo-blood group system. Blood 2013; 21 (8): 1459-1468.

[L106]

Who dreams up the idea of making extracts from snail eggs to try testing on human red blood cells?!?

No disrespect indended towards the researchers that Malcolm named, but Mabel's post was my second thought when I read Malcolm's interesting explanation of FORS1

My first thought was "Somebody has too much free time on their hands."

Donna

[Malcolm Needs ☆]

A (very) short explanation of why those with too much time on their hands did this work can be found on pages 58 and 59 of Race RR, Sanger R. Blood Groups in Man. 6th edition. 1975. Blackwell Scientific Publications (still one of my favourite books, albeit well out of date, but not least because both authors signed my copy for me).

There is a lovely bit in this section, where they say, "Here we cannot resist noting the not very practical finding by Tippett and Teesdale of an anti-B-like agglutinin in the plasma of one of the two, untinned, coelacanths they tested."

Fortunately, both Patricia and Phyllis went on to do much better things in Transfusion Science!!!!!!!!!!!!!!!!

[Malcolm Needs ☆]

FORS1 is the only antigen in the 31st Blood Group System, FORS. In 1987, three English families were shown to have members whose red cells were strongly agglutinated by the extract from the ova of the snail Helix pomatia, but not by Dolichos biflorus. The phenotype was called Apae. My friend and colleague, Bob Stamps has been following at least one member of these families for many years (a donor) and, evenutally, got the Swedish group interested. It was found that, what the family were expressing on their red cells was, in fact, the Forssman antigen, and was genetically seperate from the ABO locus.

Alpha3GalNAc, when attached to the H carbohydrate confers the A antigen, but alpha3GalNAc attached to the P carbohydrate confers the FORS1 antigen. Some polyclonal, but not monoclonal, anti-A reagents cross-react with the FORS1 antigen, which is why I had the sudden thought, but I doubt very much if my sudden thought has any milage whatsoever, as so few people use polyclonal anti-A these days.

Um, I've read the paper in a bit more detail, and it would appear that some monoclonal anti-A reagents do react with FORS1, albeit extremely weakly.