Rare Antigen

[adika1]

Hello All. I had wanted to discontinue an old procedure we had, where the nurses during order entry must indicate if the patient had been pregnant in the last 6 months, or if they have been transfused within the last 90 days. The techs are supposed to perform a full crossmatch when any of those questions are answered yes. I told my techs that they can check the patients history as always and lean on the right side by perfoming a full crossmatch if the do not feel comfortable with the IS only at anytime during a workup. One of the techs, said that she had 2 instances in the past, where a rare antigen did not show up on the screen. As she indicated if she had not done a full crossmatch she would not have know the patient wasnt compatible to the unit since the screen did not catch it. How could that be possible?

Edited April 14, 2010 by adika1
typo

[BSIPHERD]

I think you mean an antibody to a rare or low incidence antigen. This could occur when such antigens are not on the screening cells used for the antibody screen. In our experience, antibodies to Kp(a) and Cw most frequently fall into this category. You could also have Bg antibodies, particuarly with Gel that are not rare, but Gel is very good at picking them up. These aren't the only ones but are some of the most frequent. The risk of this is present even if the patient has not been transfused or pregnant recently.

Oh, just another thought. When we went to I.S. Crossmatches, we changed our requirements for the cells we use for antibody screening. We require that at least one of the screening cells have double dose Jk(a), Fy(a), c, and E.

All of us that do Immediate Spin or electronic crossmatches (probably most of us) have made the decision that even though we know these situations exist, we know that significant clinical harm based on this is very rare. Hope that helps.

Belva in Lincoln

[Malcolm Needs ☆]

I agree with what Belva says entirely.

:):):)

[adiescast]

There is always a risk for incompatibility, even if the Coombs crossmatch is non-reactive. The question is what level of risk can you be comfortable with. Most of us have a pretty good comfort level with a negative screen (against homozygous cells for the antigens Belva listed) and ABO matched units.

If you look at some of TimOz's postings about matching your screening cells to your patient population, you could get very uneasy about the risk level in a non-caucasian population.

[adika1]

Thanks you so much Belva and the rest for your response. I was really helpful.

[jayinsat]

It's interesting that we just had a patient last week whose antibody screen was negative on gel and crossmatch negative immediate spin. The patient had a reaction to the 2nd unit during dialysis. The post transfusion sample was visibly icteric (pre was clear). In light of that, an AHG gel crossmatch was performed on the unit with pre and post samples and were found to be incompatible 2-3+. DAT was negative. A rare ag panel was run and anti-Kpa was found in the sample. The offending unit was typed and found to be Kpa positive. This is only the second time in over 20 years of performing blood bank that I have encountered this incident. The first was with Redelberger. All that said, I think it would be overly cautious to perform complete crossmatches on every patient for such rare incidents, even if they had been pregnant or transfused within the last 6 months.

[Malcolm Needs ☆]

It's interesting that we just had a patient last week whose antibody screen was negative on gel and crossmatch negative immediate spin. The patient had a reaction to the 2nd unit during dialysis. The post transfusion sample was visibly icteric (pre was clear). In light of that, an AHG gel crossmatch was performed on the unit with pre and post samples and were found to be incompatible 2-3+. DAT was negative. A rare ag panel was run and anti-Kpa was found in the sample. The offending unit was typed and found to be Kpa positive. This is only the second time in over 20 years of performing blood bank that I have encountered this incident. The first was with Redelberger. All that said, I think it would be overly cautious to perform complete crossmatches on every patient for such rare incidents, even if they had been pregnant or transfused within the last 6 months.

This is a very interesting case Jayinsat.

Have you read Koshy R, Patel B, Harrison JS. Anti-Kpa - induced severe delayed hemolytic transfusion reaction. Immunohematology 2009; 25: 44-47.

This is the first case report published that implicates anti-Kpa in a severe delayed haemolytic transfusion reaction.

:confused::confused:

[adika1]

Whoa!!. Thanks for sharing. Scary...

[galvania]

Here in Switzerland it is obligatory to have a Kpa+ cell on the screening cells

[Malcolm Needs ☆]

Here in Switzerland it is obligatory to have a Kpa+ cell on the screening cells

If I remember correctly (and these days that is becoming an increasingly rare event, because of the advancing years), this used to be true in the UK too. I think that in the 1996 Guidelines, Kp(a+) screening cells were, at the very least, encouraged, but in the 2004 Guidelines this was not so.

I'll check.

:):)

Yep, as usual I was wrong! The 1996 Guidelines don't mention the Kp(a) antigen on screening cells, but the 2004 Guidelines specifically say that the Kp(a) antigen is not required.

I wasn't that far out though!

:redface::redface:

Edited April 19, 2010 by Malcolm Needs

[Steven Jeff]

That said Malcolm, the Kp(a) antigen is present in the 3 cell screen provided by the NBS. I am sure I am correct in that, I am at home.

Steve

:)

[Malcolm Needs ☆]

That said Malcolm, the Kp(a) antigen is present in the 3 cell screen provided by the NBS. I am sure I am correct in that, I am at home.

Steve

:)

Yes, you are quite right Steve. It is just that it is there as a "bonus" (as it were); it doesn't actually have to be there.

:(:(

[galvania]

It never ceases to amaze me how much divergence there is within Europe as to what is considered essential in one country and not at all required in another. And no, I am not talking about things like Mia or Dia which are relevant in some parts of the world but far less in others. Even simple things like which cells you have to use for reverse typing - A1/B in some places; A1/B/O in others; A1/A2/B/O. ** hum - nice that Europe is so united (ha-ha).

[galvania]

Me again - I don't know where the asterisks came from in my last contribution???????

[Malcolm Needs ☆]

It never ceases to amaze me how much divergence there is within Europe as to what is considered essential in one country and not at all required in another. And no, I am not talking about things like Mia or Dia which are relevant in some parts of the world but far less in others. Even simple things like which cells you have to use for reverse typing - A1/B in some places; A1/B/O in others; A1/A2/B/O. ** hum - nice that Europe is so united (ha-ha).

Agreed - and that is with the European Directive. What would it be like without it???????!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

:eek::eek:

[Steven Jeff]

It never ceases to amaze me how much divergence there is within Europe as to what is considered essential in one country and not at all required in another. And no, I am not talking about things like Mia or Dia which are relevant in some parts of the world but far less in others. Even simple things like which cells you have to use for reverse typing - A1/B in some places; A1/B/O in others; A1/A2/B/O. ** hum - nice that Europe is so united (ha-ha).

Hi Anna

My routine Group & screen comprises of an Ortho BioVue Card with anti-A; anti-B; 2 anti-D's; anti- K (because it is there and useful) and a reagent control. A1; B and O cell reverse group and a 3 cell antibody screen. The O cells are not really essential but it suits our workflow.

It would be interesting to see other combinations and why

Steve

:)