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Repeat Antibody Investigations


richj

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Hello

What is the policy at your facility regarding repeat antibody investigation? Is it possible to introduce rules to reduce unnecessary testing and reduce costs without impacting patient safety. 

Take frequent flyer Cancer Clinic patients who come in once a week. Patient has Anti-E ...Same lot # screening cells, no variation in strength, regardless of transfusion ..can you eliminate the panel and perform a gel compatible crossmatch with E- units. 

Thanks

Richard

 

 

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4 minutes ago, Malcolm Needs said:

I must admit that makes me nervous Teristella.

All our antibody pos patients get 2 units extended crossmatched, whether there are orders or not - or 2 units in addition to any orders.

 

Does the hospital that doesn't perform a new panel for 30 days not make you nervous? 

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In answer to your last sentence Teristella - GOOD LORD YES!

Turning to your first sentence, the problem with performing an extended cross-match is that, if, for example, the patient has either sprouted a weak anti-Fya, or worse, has made an anti-Fya in the past (unrecognised), but has not been re-stimulated for a long time.  Either the units could both be Fy(a+b+), or one could be Fy(a+b+) and the other Fy(a-b+), and the cross-match may not detect it.  This is because the red cells in the antibody identification panel are in a preservative that maximises the expression of the red cell antigens, but NOT the oxygen carrying capacity of the red cells, whereas the red cells in the units are in a preservative that maximises the oxygen carrying capacity of the red cells, but does not maximise the antigen expression of the red cells (and the Duffy antigens are known for deteriorating upon storage (as are the Knops antigens, but they don't matter).  So, by cross-matching without performing a panel, you may be missing an anti-Fya, and if the screening cell that is Fy(a+b-) may have come from an individual who has the FYA/FY genotype, if these red cells have come from a donor of the Black ethnicities, but the human immune system is MUCH more sensitive than our tests, so you have a DHTR on your hands.

This, however, is purely a personal point-of-view.

Edited by Malcolm Needs
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3 minutes ago, John C. Staley said:

I'm stretching the memory cells here but I believe that if there were no changes in the antibody screen and the AHG XMs were compatible we did not do a panel and this met the AABB Standards AT THE TIME.  This may have changed and it would not surprise me if it did.  

If I am reading these responses correctly, I would suggest that it is at least possible that there could be a weak developing allo-anitbody that would  easily be obscured by a 'mere" 2 or 3 cell screening (that has positivity that matches the previous sscreen).  In which case, just because a new positive screen re4activity matches the previous one, one cannot rule out other newer significant antibodies, as you may be able to do with a full antibody ID workup involving panels.

Getting back to the original posts, we would attempt to have the patient phenotyped to start with.  Then for transfusions, we would only give those phenotypically-matched units.  As long as we keep this up, we can be reasonably certain that no new antibodies are going to sneak in (as long as we are the only facility transfusing the patient!).  This is the approach we try to take for particular patients with multiple antibodies, warm autos, Daralex patients etc.

Scott

 

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20 hours ago, John C. Staley said:

I'm stretching the memory cells here but I believe that if there were no changes in the antibody screen and the AHG XMs were compatible we did not do a panel and this met the AABB Standards AT THE TIME.  This may have changed and it would not surprise me if it did.  

The standards simply state "additional testing must be performed" and I had previously pointed this out to my supervisor but it never went anywhere. Their Guidelines for Antibody Identification seem to indicate that facilities can vary the frequency as long as there is a set policy, but of course the wording is pretty vague. We haven't been initially AABB inspected yet, but we'll see what happens.

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5 hours ago, Teristella said:

The standards simply state "additional testing must be performed" and I had previously pointed this out to my supervisor but it never went anywhere. Their Guidelines for Antibody Identification seem to indicate that facilities can vary the frequency as long as there is a set policy, but of course the wording is pretty vague. We haven't been initially AABB inspected yet, but we'll see what happens.

We considered the AHG crossmatch as "additional testing".  If any antigen negative units to previous identified antibodies, showed an incompatibility then a full panel was completed and more if indicated at that point.

Edited by John C. Staley
attempted some clarification.
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Once a specificity has been definitely identified, there is no requirement to "re-identify" it every time you receive a sample.  You may want to test to see if it is still detectable, but that can be done using a single red cell sample.  However, as screening red cell phenotypes tend to be complementary, I still contend that a panel should be performed (albeit, it may be an abbreviated panel), to ensure no de novo specificity has developed.

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3 hours ago, Malcolm Needs said:

Once a specificity has been definitely identified, there is no requirement to "re-identify" it every time you receive a sample.  You may want to test to see if it is still detectable, but that can be done using a single red cell sample.  However, as screening red cell phenotypes tend to be complementary, I still contend that a panel should be performed (albeit, it may be an abbreviated panel), to ensure no de novo specificity has developed.

Right, good point.  The previously ID'd antibody does NOT need to be "reproved" (even if it is not showing up you will be screening units for it anyway).  But any newly developed (i.e. de novo - Spanish for "not vocal" BTW) must be ruled out each time.  Assuming they do not exist because a screen panel of 2 or 3 cells "matches' previous screen results just isn't adequate as far as appropriate "additional testing" that "must be performed".

Scott

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I always want testing of patients with antibodies to be as sensitive to detect new antibodies as the screen is for patients with no antibodies.  That means, for all usual specificities, I want to run a double-dose cell (from homozygous donor) that is negative for the antigens that known antibodies are directed toward whenever possible.  I am comfortable mimicking the screen cells (single dose K cell, but double for the other "usual suspects").  In the face of multiple antibodies, it is not always possible to test all of the desired specificities with double-dose cells, but I want to come as close as I can. 

We just had an O neg "frequent flier" (with prior anti-C) transfused on 7/26 make a new anti-E found on 8/14.  Auto control negative (so it either was not very avid or already destroyed the E+ unit).  That's 18 days,  Had it been covered up by an antibody that reacted strongly with both screen cells, we might not have found it without the panel cells if the antigen on the crossmatched cells was not particularly strong and the antibody was pretty weak (like Malcolm said).

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Our policy is if the patient is transfused they get a new ABID every 3 days but if the patient is not transfused we will only do the ABID if they are going to be transfused or every 7 days which ever comes first.  Being at a children's hospital we don't get a lot of antibodies and most of them are WAA from our oncology/hematology kids.  Plus we don't have the staff to complete the WAA workups ourselves and they get sent to a reference lab.  So if they are just keeping a current TSCR but are not planning on transfusing (usually they give medication instead of transfusing these WAA kids) we only send out the ABID if they want blood for a procedure or something.  We also keep the kids on the same unit and/or donor as long as possible.  That's the nice thing about kids.  For those kids with other than WAA we do a new ABID with every sample.  For neonates (passive antibodies) we do a new ABID when we run out of specimen to crossmatch new units which happens rarely.

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