anti-E?

[WAAlover<3]

We had a patient come in that had a history at our hospital of an anti-Bga. This was from AHG tube testing using LISS. We now use capture technology on an Echo and the patient came in again. Screening cell two on the Echo was positive. Our SOP is to then do a ReadyID panel and a DAT also on the Echo. The DAT was negative and all E+ cells showed reactivity on the panel. (Screening cell 2 was also E+.) We then did two AHG phase crossmatches on the Echo which were both compatible. The problem came when we phenotyped the patient. They typed as E+…as did both units that were crossmatched. Our manager ended up calling it an autoantibody with anti-E specificity. I am fairly new to blood banking but wondered why she called in an autoantibody if the patients DAT was negative. I believe I read something that a person can create a non-red cell stimulated anti-E but could cross react with red cell-bourne structures. I was just wondering what everyone out there thinks about this or if anyone could just shed some light on this for me. Thanks!

[Eagle Eye]

you probably need to send patient's specimen for molecular typing. We had a patient who was C+ and made anti-C but DAT was negative. ...I think similiar to partial D///

[Malcolm Needs ☆]

Your DAT may have been negative, but it depends upon several factors as to why this was so when the patient was E+ themselves, and why the two E+ units appeared compatible.

Firstly, it will depend upon what anti-immunoglobulins are in your AHG.

There is a very good chance that such an antibody will be (mostly) IgM, but an IgM that does not trip the complement cascade. If your AHG does not have a decent amount of anti-IgM in it, the DAT will be negative (as would the cross-match with the 2 E+ units).

Secondly, it will depend upon the "fit" of the antibody to the antigen.

Very often, such antibodies are "naturally occurring" (although, of course, there must have been some undefined stimulus). Such antibodies do not "fit" their corresponding antibodies as well as "genuine" immune specificities, and so the antibody-antigen complex can be quite fragile.

This is true of early immune antibodies too. An IgM anti-D in a recently immunised patient can, in some circumstances, also have an element of a mimicking anti-I, but once the IgG production phase has kicked in, the anti-D "fits" the D antigen much better (becomes more specific) and the anti-D will no longer exhibit the mimicking anti-I specificity.

It is a difficult concept, I agree!

The third thing to take into account is that the screening cells are kept in a preservative that is designed to keep their antigenicity at an optimal level, but not their oxygen carrying capacity.

The units, on the other hand, are kept in a preservative to keep their oxygen carrying capacity at an optimum level, but not their antigenicity.

The screening cells may well have a "double dose" of the E antigen, whilst the units (and/or the patient) may have a "single dose" of the E antigen (anti-E can quite often show dosage).

Did you try enzyme treating the patient's red cells and those of the units? The anti-E may well be shown to be an auto-antibody by this method, and the red cells from the units may well have been "incompatible" by this method.

The anti-E may have been a mimicking anti-E, that is an extremely weak panagglutinin to a very common Rh antigen, such as Rh17 or Rh18, but which reacts preferentially with the E antigen.

Lastly, there was a very good paper in Brit J Haem that might be worth a read.

Sachs UJH, Roder L (the "o" has an umlout - or however you spell it - but I can't do this on here!), Santoso S Bein G. Does a negative direct antiglobulin test exclude warm autoimmune haemolytic anaemia? A prospective study of 504 cases. Brit J Haem 2006; 132: 651-661.

I hope that is of some help.

:):)

[mjshepherd]

My first question with showing an E specificity with a positive E antigen type would be when was the last time they were transfused. We had a case of a new anti-E found on the night shift that confused the tech to no end because she was typing E positive. After getting a better history we found out she had gotten 4 units the prev month at another hospital and were picking up donor cell reactions.

[Mohandoss Murugesan]

very useful explanation

[Malcolm Needs ☆]

My first question with showing an E specificity with a positive E antigen type would be when was the last time they were transfused. We had a case of a new anti-E found on the night shift that confused the tech to no end because she was typing E positive. After getting a better history we found out she had gotten 4 units the prev month at another hospital and were picking up donor cell reactions.

Surely though, unless it was a child or an adult of small stature, there would have been a mixed-field reaction with the anti-E grouping reagent????????

:confused::confused:

[mjshepherd]

Believe it or not Malcom it was a strong 2+ reaction with Monoclonal anti-E, we sent to reference for confirmation and it was confirmed after cell seperation that the patient was E negative.

[Malcolm Needs ☆]

Believe it or not Malcom it was a strong 2+ reaction with Monoclonal anti-E, we sent to reference for confirmation and it was confirmed after cell seperation that the patient was E negative.

Thanks for that; interesting results!

It does rather confirm, however, that the anti-E was alsmost certainly not clinically significant, otherwise all of those E+ red cells (or, should I say, a lot of those E+ red cells) would have been removed from the circulation by the RES.

:confused::confused:

[Yanxia]

Thanks for that; interesting results!

It does rather confirm, however, that the anti-E was alsmost certainly not clinically significant, otherwise all of those E+ red cells (or, should I say, a lot of those E+ red cells) would have been removed from the circulation by the RES.

:confused::confused:

And the DAT will be mix field positive, at least 2+mf.

[Malcolm Needs ☆]

That's true.