Immediate spin crossmatches

[JohnT]

Hi Sandi

Interesting thread - but this comment would worry me 'If they get a patient with a positive screen they have to send out the patient specimen and segments from the units they want crossmatched for antibody ID and unit antigen testing.' My understanding of what you are saying is that they are asking another facility to test their units and to crossmatch them, but retaining the units on-site. It seems to me that the potential for identification errors in this procedure is sufficient to nullify any benefits. Surely it would be safer for the testing laboratory to identify suitable units and send those to the hospital.

Any comments?

John

[Malcolm Needs ☆]

Hi Sandi

Interesting thread - but this comment would worry me 'If they get a patient with a positive screen they have to send out the patient specimen and segments from the units they want crossmatched for antibody ID and unit antigen testing.' My understanding of what you are saying is that they are asking another facility to test their units and to crossmatch them, but retaining the units on-site. It seems to me that the potential for identification errors in this procedure is sufficient to nullify any benefits. Surely it would be safer for the testing laboratory to identify suitable units and send those to the hospital.

Any comments?

John

I totally agree with you John.

Nobody in my own Laboratory would dream of cross-matching units from segments other staff in my own Laboratory had snipped off from units, let alone segments snipped off from elsewhere. It is a recipe for a disaster!

[Dr. Pepper]

We use the Immucor screening cells. You can get them in a Cw+ version. Our current lot has homozygous doses for all Rh, Duffy, Kidd and MNSs antigens. Once in a while you might not get a S homozygous cell, but they're pretty good about the others. Last year we had our first reaction since we started IS crossmatches due to a "missed" antibody (anti-Wra), so I wonder if antibodies to low-incidence antigens not found on the screening cells could be more of a problem than missing weak antibodies due to heterozygous doses of antigens on the cells or using LISS vs. gel, etc. And let's see you find screening cells that are homozygous for K.

By the way, I believe that Boral and Henry used a 2 donor pooled screening cell, pretty insensitive by today's standards.

[Malcolm Needs ☆]

. Last year we had our first reaction since we started IS crossmatches due to a "missed" antibody (anti-Wra), so I wonder if antibodies to low-incidence antigens not found on the screening cells could be more of a problem than missing weak antibodies due to heterozygous doses of antigens on the cells or using LISS vs. gel, etc. And let's see you find screening cells that are homozygous for K.

Not according to an Editorial written for Transfusion by George Garratty (Garratty G. How concerned should we be about missing antibodies to low incidence antigens? Transfusion 2003; 43: 844-847).

In this, George reports that, in a study published by Arriaga et al in 2001 in which it is reported that over a 10-year period, when 300, 000 units of RBCs were transfused, only three HTRs due to anti-Wra were encountered.

He also wrote about some studies published by Shulman in 1990 that concluded "Thus, the risk of an overt HTR associated with antibody to a low incidence antigen was 1 per 650, 000 crossmatches."

I'm happy to go along with george on this one!

[Sko681]

I totally agree with you John.

Nobody in my own Laboratory would dream of cross-matching units from segments other staff in my own Laboratory had snipped off from units, let alone segments snipped off from elsewhere. It is a recipe for a disaster!

I agree as well! At my hospital we have a similar scenario where we are considered the "reference lab" to two other facilities that do not do antibody identification. What we do is have a second properly labeled specimen sent to us which we do the AB ID on and screen units. We double check to make sure the units are compatible and then send the units over to the appropriate facility. Once the units are at the appropriate facility they are re-crossmatched using the original specimen (which is banded) or a new specimen depending on collection date.

~Shaunna

[Dr. Pepper]

Thank you Malcom. I believe Boral and Henry's "miss" rate was 1 in 10,000 with pooled 2 cell screening cells. After doing IS crossmatches for years I figured we were overdue. But 1 in 650,000.....Some ladies feel they're lucky when they meet Mr. Right; our tech however, could not be numbered among them.

[Malcolm Needs ☆]

Well, 1 in 650, 000 is what the Editorial says (and I had it front of me when I quoted it).

[Packer Banker]

Last year we had our first reaction since we started IS crossmatches due to a "missed" antibody (anti-Wra), so I wonder if antibodies to low-incidence antigens not found on the screening cells could be more of a problem than missing weak antibodies due to heterozygous doses of antigens on the cells or using LISS vs. gel, etc. And let's see you find screening cells that are homozygous for K.

I'm thinking that the incidence of the low incidence antigens, and the even lower incidence of the antibodies, would make it MUCH LESS of a problem. I think homozygous expression of the antigens on the screeing cells is by far more valuable when it comes to the safety of the transfusion.

Our policy at our hospital is to do IS XMs- of course only when there is no history of a positive screen. Most people there, however, feel uncomfortable with that and do a coomb's XM. Where I used to work, we did electronic XMs. I do miss those- especially in hurried OR or emergency release situations.

[Packer Banker]

Sorry- that was a pretty much a duplicate (although I hadn't the stats to back it up like that!)- I hadn't yet made it to the end of the thread...

[Mabel Adams]

What is EDTA saline? I've not heard this used in the US. Why would the IS XM be hard to standardize? To what standard is it being compared?

The function of the IS XM is to detect ABO incompatibilites that were otherwise overlooked. It will never detect alloantibodies of the usual sort for which an AHG screen & xm are used. It will mostly detect rouleaux and cold agglutinins--not desirable or significant, but time-consuming. As an ABO comptibility check the electronic crossmatch is probably better because it does just as well at detecting ABO incompatibility between patient and donor, is not subject to delays caused by false positives as above, isn't prone to technical errors like using the wrong patient sample or forgetting to add sample and doesn't mislead techs to think they are able to detect incompatibilities to alloantibodies by it.

[Mabel Adams]

Sorry, I keep posting before I get to the last page--always did tend to spout off too soon.

About segments sent from other hospitals: where I used to work we used to do that so we could antigen type the units for them from those segments--they were expected to do the antiglobulin crossmatches themselves. In rural Idaho, this saved a lot of time and transport difficulties. You are correct that they have to be very careful about the segment labelling for this to work. Once the screen went negative and they needed screened units but did not need to send us a specimen, they would just request the screened units be sent from our stock as there was no savings in time by them sending segments from their units. This would help ameliorate the biggest risk--wrong antigen-typing on a unit that the AHG xm could not detect. Not perfect, but 24 hr delays of transfusion have risks too.

[Malcolm Needs ☆]

I'm thinking that the incidence of the low incidence antigens, and the even lower incidence of the antibodies, would make it MUCH LESS of a problem. I think homozygous expression of the antigens on the screeing cells is by far more valuable when it comes to the safety of the transfusion.

QUOTE]

Hi Jennifer,

I'm very sorry, but I must disagree with the statement I've changed into red (the rest I agree with 100% or more).

Actually, if you look for them, and I would NOT recommend that you so do, antibodies directed against low incidence antigens are surprisingly common; it's just that they are rarely detected because the screening cells very rarely express the antigens (indeed, in the UK, we type the screening and panel cells for Wr(a) and deliberatley exclude any that are positive).

We had an Lu: 8, 14 cell on one of our panels not too long ago (by utter bad luck) and we picked up two cases of anti-Lu14 in two weeks; a blank, blank nuisance, I might add!

[Malcolm Needs ☆]

What is EDTA saline? I've not heard this used in the US. Why would the IS XM be hard to standardize? To what standard is it being compared?

The function of the IS XM is to detect ABO incompatibilites that were otherwise overlooked. It will never detect alloantibodies of the usual sort for which an AHG screen & xm are used. It will mostly detect rouleaux and cold agglutinins--not desirable or significant, but time-consuming. As an ABO comptibility check the electronic crossmatch is probably better because it does just as well at detecting ABO incompatibility between patient and donor, is not subject to delays caused by false positives as above, isn't prone to technical errors like using the wrong patient sample or forgetting to add sample and doesn't mislead techs to think they are able to detect incompatibilities to alloantibodies by it.

Hi Mabel,

EDTA saline is sort of what it says on the label; it is saline that has EDTA added to it. This is used in the IS XM to suspend the red cells so that it inhibits complement in the serum to which they are added (it doesn't matter if you are using EDTA plasma), as C1 can cause steric hinderance of ABO antibody attachment, causing a prozone and, therefore, the danger of a false negative result. Thus, blood of the wrong ABO group could be transfused.

I agree with you entirely that electronic issue is safer than a serological cross-match, because it does not involve human error, but, if the situation is so urgent that an IS XM is required, electronic issue would not be allowed in the UK, because we only allow it if a) the sample has been typed on automation and the results transmitted without human intervention, there are two types the same and c) there are no clinically significant atypical alloantibodies either in the present sample or in the patient's history (there are lots of other rules governing its use, but these are the main three in this instance).

I would contest that, in such an emergency situation, none of these criteria could be met.

Obviously, I am not sure of the rules governing electronic issue in other countries; being notoriously parochial!!!!!!!!!!!!!

:)