Unexplained Antibody Screening Results

[BankerGirl]

I had a trauma patient (auto accident) come in this morning who took 2 O Neg and 2 type specific uncrossed units. His antibody screen is positive in gel with all three screening cells. The reactions were mixed (4+ with a very tiny button in the bottom of the wells). The antibody panel, Autocontrol, DAT, and Immediate spin and AHG crossmatches on 8 units were completely negative. We use diluted Immucor cells for the type and screen, but Ortho Panel A for the antibody ID. I repeated the antibody screen with PeG and all 3 cells were weak 2+ positive. I thought it might be an antibody to the Ortho diluent , so I washed the screening cells with saline, resuspended them in Ortho diluent, and the result is exactly the same as the first time I ran it. The patient has since been transfered to a larger trauma center, and I barely have any plasma left, so my further testing options are limitted. What can this be?:cries::cries:

[Malcolm Needs ☆]

It could still actually be something in the Ortho diluent.

If, as I suspect, the diluent contains sime form of antibiotic to stop bugs growing, this can bind quite firmly to the red cells (washing them will not necessarily dislodge these molecules), and if the patient has an antibody to the antibiotic (either specific or cross-reacting) you may still see agglutination. The small number of "negative" cells at the bottom of the column represents a few red cells that have not bound "as much" of the antibiotic.

DiaMed in Europe are well aware of similar findings.

It is comparatively rare, but not unknown.

[cassinnc]

Are you using Immucor screening cells for your tube testing also? If you think the problem is with your diluent, then I would not use the diluent to resuspend the cells after washing them. If you are using Immucor cells in the tube and the Gel, I would try using another manufacturer such as Ortho for the antibody screen if you have them. If you have Immucor panel cells, I would run a few of them also. If all Immucor cells come up positive and other manufacturers come up negative, then you can assume that the patient's plasma is reacting with a component in the Immucor reagents. I hope this makes sense and helps.

[BankerGirl]

Well, I liked Malcolm's explanation about the antibiotics binding strongly, and since I do not have another manufacturer's screening cells, I ran 4 Immucor panel cells in gel. Same diluent and antibiotics as the screening cells. All 4 are as negative as can be. The tech at the hospital where we transfered the patient has one screening cell positive in her workup, but I wasn't here when she called so I don't know what manufacturer they use. I am throwing in the towel and going home for the day.

[cassinnc]

Sorry you had a bad day! I have had to throw in the towel on some of these type things myself. If the other facility comes up with something, can you post it? I am curious to know how this comes out.

I hope you have a better day tomorrow.

[rravkin@aol.com]

Malcolm, do they not use the same antibiotics in the panel cells? If so, why was the panel negative?

These are very strong reactions and I would suspect fibrin formation in the plasma but I would have also expected similar reactions with the panel cells. Non-the-less, did you try respinning the patient specimen and repeating the screen? Did you get a diagnostic history on the patient including current medications? Also, and not to leave a stone unturned, did you check the expiration date and viability of your screening cells? Furthermore, would you consider repeating the Ab screen using a different in-dated set of screening cells?

Edited October 29, 2010 by rravkin@aol.com

[Malcolm Needs ☆]

Hmmm, with the panel cells showing negative results, it looks like I'll have to put my thinking cap back on (and my head hurts after yesterday's audit)!!!!!!!

[BankerGirl]

Well, another day brings another stab at this puzzle. The screening cells were nearing their expiration date, but QC was fine and all other patients tested negative (lucky, huh?). Today I ran the specimen with the new screening cells and all three were negative as can be. The question now: is it negative because of the new cells or because of the 24 hours it sat in the refrigerator? Since I insist on beating this dead dog, I repeated it with the previous lot, and the cells are 4+ as before. Obviously this has to be something about that lot of screening cells, but it is just killing me that I can't figure out what it is! I think I will have to live with not knowing though--something I am not very good at!:frown::frown:

[AMcCord]

Well, I was going to suggest that the specimen might have been drawn right after the patient had a radiology procedure with contrast media or IV infusion of something interesting - but your last post throws that completely out the window. Definitely weird.

[kitty]

Learn something new everyday....

[goodchild]

I know we've gotten also gotten some strange results with our ortho screening cells, particularly when they are nearing the expiration date. The manufacturer recommended keeping them cold and keeping them in the dark as much as possible and that has helped a lot.

[LaraT23]

Does anyone think that maybe we are seeing some low incidence present on the first lot of screen cells and not on the panel or the new lot? I have had that happen, and just call it "IgG non -specific" and go on with AHG crossmatches.

I have also had the antibiotic issue, but did find that all panel cells were also reactive. I have two documented patients who made antibodies to the antibiotic, one patient stopped taking their antibiotics, and three weeks later, no more reactions.

[Eagle Eye]

can you run DAT on screening cells? It's very less likely you will have positive DAT on all three. Once in a while we see this one cell not all three. But it doesn't hurt to try!!!!

[rravkin@aol.com]

BankerGirl,

It is possible that the original plasma tested with the screening cells was contaminated with platelets and or white cells. Since we add the screening cells first to the columb followed by the plasma, platelet and or WBC's would migrate to the surface of the gel after a population of the screening cells had a chance to migrate into the gel. Thus after testing is completed the cells that were able to migrate into the gel prior to the platelet and/or WBC sealing off the surface of the gel would be at the bottom of the colomb and the rest would be sequestered at the top producing a 4+ mixed feild reaction. The plasma tested twenty four hours later would be platelet and/or WBC poor and therefore produce negative results. This senario would have also potentially occured with fibrin stands as well. Still, the burning question is why didn't we see similar results in at least one of the panel cells tested? A likley possibility is that there was indeed a plasma contaminant, ie platelets, WBC's, of fibrin strands, such that one or more were present in the reaction volume of the antibody screening tests and approximately 30 minutes later when the testing was complete, the contaminant settled out enough so that it would not be present in the reaction volume of the panel cells. Given the information provided this is a very likely cause. I hope this helps a little bit. :)

Edited October 30, 2010 by rravkin@aol.com

[Yanxia]

I learn things more in this thread.

I agree with the low incidence antigen suspecious.

And I have a new idea, it is an antibody against old red cells. During the cells ageing, the lipid on the cell's surface will lose, then will expose some new antigen, so we will find some odd reaction with old cells.

[Malcolm Needs ☆]

I don't think it is the result of an antibody directed against a low incidence antigen (or, indeed, a "soup" of such antibodies) in the patient's plasma Lara, as one of the screening cells may well express such an antigen without anyone knowing about it, but all three? Even if each expressed a different low incidence antigen, the odds against it would be astronomical (but, I must admit, not impossible).

[LaraT23]

Too true malcolm. I also think the age of the screen cells has something to do with it. Old screen cells start to look ugly, and are definitely suspicious on their last day. I would say go the DAT route, only all patients tested would be positive with DAT pos screen cells. The full crossmatch should catch most things that might be an issue. So, just go with a neg screen ( new cells attested to that) and then cautiously do full crossmatches.

[AMcCord]

Are you cozy with Micro? How about a culture on the old cells? Maybe there is bacterial contamination - weird things can happen with that. Your new lot of screen cells are clean and your panel cells are clean, so no reaction with them -????

[Yanxia]

I don't think it is the result of an antibody directed against a low incidence antigen (or, indeed, a "soup" of such antibodies) in the patient's plasma Lara, as one of the screening cells may well express such an antigen without anyone knowing about it, but all three? Even if each expressed a different low incidence antigen, the odds against it would be astronomical (but, I must admit, not impossible).

You are right, Malcolm.

[Yanxia]

Are you cozy with Micro? How about a culture on the old cells? Maybe there is bacterial contamination - weird things can happen with that. Your new lot of screen cells are clean and your panel cells are clean, so no reaction with them -????

I don't think it is because bacterial contemination, because not all the test use this lot of cells is positive, in reality only this patient give the positive reaction.

And aakupaku mentioned above to do DAT of the screening cells, I don't think it is a good method, the reason is the same as above.

[rravkin@aol.com]

BankerGirl,

Were the Panel Cells approaching their expiration date as well? If not when do they expire in comparison to the screening cells.

And for the other posters; how does the anomaly antibody explain post #8 of this thread, the 4+ mixed field reactions, and the absolute lack of reactivity in any of the panel cells? I would be more confident in this theory if the reactivity were no greater then 2+ and if we saw any reactivity in the panel cells; or given that the screening cells were 4+ mixfield and any equal reactivity in the panel cells.

[kitty]

How about cross contamination of your screening cells?? Just throwing it out there...

[John Eggington]

What do you use to control antibody screens (e.g. weak anti-D with each batch of tests, etc.) and how did these controls perfrom on the day of the original investigation?