Unusual Typing Results

[Dr. Pepper]

This case had a twist and turn to it for us. A pre-op patient for surgery next week typed as follows:

anti-A 4+

anti-B 3+

anti-D 3+

Rh Control 0

A1 cells 0

B cells 2+

What could cause these reactions, and how would you eliminate the possibilities?

[Malcolm Needs ☆]

Well, one obvious thing is that the patient has an antibody directed against an antigen expressed on the reverse grouping B cells that is not expressed on the reverse grouping A cells, and you could eliminate this by performing a full panel at room temperature, and then using reverse grouping B red cells that do not express this antigen.

However, it could easily be a case of acquired-B, in which case you could lower the pH of the ABO typing, use an anti-B that is known not to detect an acquired-B antigen, and use a known case of acquired-B as your group B reverse grouping cells.

After that, I'll have to have another (serious) think!

[Liz]

I agree with you Malcolm. I use this as an oral exam question. But Malcolm is an anti-B that is known not to detect an acquired-B antigen a reagent? And how does a "a known case of acquired-B as your group B reverse grouping cells" help?

[Malcolm Needs ☆]

Hi Liz,

Following as case in the US several years back, involving clone ES4 (Garratty G, Arndt P, Co A, Rodberg K, Furmanski M. Fatal hemolytic transfusion reaction resulting from ABO mistyping of a patient with acquired B antigen detectable only by some monoclonal anti-B reagents. Transfusion 1996; 36: 351-357), it was advised that the pH of monoclonal anti-B reagents should be adjusted (at source, by the commercial companies, if I remember correctly) so that they do not detect acquired B, and clones, such as ES4 were "banned", and so finding a commercial anti-B that does detect acquired B is now fairly unusual, although not unique (we still see a few, but they are now very rare).

The plasma from a known case of acquired B will react with "normal" B cells, but will not react with red cells that themselves have the acquired B - although, somewhere in the back of my mind, I seem to remember that this is only true to a certain extent. I seem to recall that, as there is more than one cause for the acquired B antigen, the anti-B will not react with the acquired B antigen if the cause of the acquired B is the same, but may react with an acquired B antigen if the cause of the acquired B antigen is different.

I know what I mean, but I'm not sure that I have put that last bit as well as I could have done! If you can't understand my ramblings, let me know and I'll give it another go.

[Malcolm Needs ☆]

By the way Phil, what is the op? Is it an abdominal procedure, because acquired B, IF that is what it is, is very much associated with gastro-intestinal diseases (about 64% of acquired B patients have gastro-intestinal disease association).

[Liz]

It is clear, Thank you!!

[dgibaud]

I know this is an outpatient preop, but I would certainly check to see if there is a transfusion history. If this patient received some A plasma or platelets recently you could see this pattern.

[Dr. Pepper]

OK, my tech on Monday asked me for guidance here. You fine blood bankers have suggested most of what we did.

1. The Rh control was negative, indicating there was no generalized false positive phenomenon going on in the front type.

2. The antibody screen was negative, which, short of a IgM antibody to a low incidence antigen on the B cells, eliminates other antibodies besides anti-B.

3. We considered acquired B, but the patient was preop for a total knee replacement and had an unremarkable CBC. In the acquired B cases I've seen, the patient had a raging sepsis, CA of the stomach or intestine or similar GI problems, and weaker reaction with anti-B than 3+ (the 3+ aroused my curiosity as we almost always get 4+ reactions with our anti-.

4. I asked her to find several patient group A specimens to see what their anti-B did with our problem cells. They were all negative. Not being acidified sera, they should have reacted to some degree with the cells if it was acquired B.

5. She washed the patient's cells which eliminated the reactivity with the reagent anti-B. Now I've taught my students for years about false-positive reactions due to an antibody to the yellow dye acriflavine in anti-B but never seen it in a patient. The lack of reactivity with patient anti-B, lack of reactivity with washed cells, negative Rh control and negative antibody screen seemed to point in this direction. So, we reported out the type as A Pos and went home.

We had a CAP inspection Tuesday and I didn't get to play with this any more until yesterday. I repeated the routine typing - and it was an ordinary group A, D- patient whose cells showed no reactivity with the anti-B! I tried a slide typing to get the most out of the alleged anti-acriflavine antibody, but no reactivity. The CBC tube was a mundane A+ as well. I checked the anti-B package insert (about time, huh?) - the yellow dye was napthol yellow, not acriflavine. So much for that idea. So what had happened?

My typing discrepancy procedure starts off with something like "REPEAT THE TYPING AND MAKE SURE YOU REALLY HAVE A PROBLEM!!!!!!!!" Did the tech do that? We seemed to remember her saying that (or did she say she repeated just the backtype) but she was at home sick the last two days and unavailable for comment. So where did that 3+ reaction with the anti-B come from? My best guess was reagent anti-D.

We do tube typings in racks, and prenumber the tubes for each typing (tube 1 for anti-A, tube 2 for anti-B etc). We may add the reagent antisera and RBCs to several sets of tubes in anticipation of imminent use but only do one typing at a time. Could she have added a drop of anti-D to tube #2 for that typing? How about other typings from that rack? If anti-D was in all the anti-B tubes, other discrepancies should have shown up. Her two previous typings done in the rack were routine O Pos. We retyped all the samples done that day, all were as they should be. So I decided to post this case, as a reminder that we sometimes make more work for ourselves than we need. I had my working hypothesis.

Until this morning, when she returned to work. Not only had she repeated the full typing, but on repeat she labeled 5 new tubes and added the reagents instead of using the next set from her prepared rack. She still got 3+ with anti-B. So the odds of her messing up twice the same way seemed very remote. She used the same patient RBC suspension for both typings. Could she have added anti-D to that tube? If so, the Rh control should have shown similar 3+ reactivity, and washing the cells should not have removed that or the reactivity with anti-B.

So, it's still a bit of a mystery. Forgive me if this is longwinded, but we serological detectives want to solve our puzzles. (I thought I had - twice.) It had to have been technical error of some sort, but I'll be da...ed if I can figure this out.

Edited September 1, 2011 by Dr. Pepper

[David Saikin]

Sometimes those are/become unsolved mysteries - can't repeat them; it seems everyone did everything right . . . you just can never resolve it . . .