Question concerning unexpected antibodies.. (from student)

[tuffgrrrrl]

Hi, there thanks everyone for help in the past btw. I love BB but it can be overwhelming when we have so many classes and I feel we really do not get enough time to soak in the material at all. Just trying to stay afloat. Ok so, I'm stumped with this case study I would appreciate any help.

A man was typed as A,B, negative. No other immunologic tests were done because the patient went into shock from blood loss and needed transfusion STAT. No antibody screen, no crossmatch was done. The bloodbank had no A,B negative blood so they gave him 6 units of O neg.

Some days later he is still "bleeding". The MD says that this patient now needs 6 more units of packed cells and 4 units of plasma. The results of ABO RH typing on UNwashed cells were as follows:

anti-A: 2+MF

anti-B: 2+ MF

A1 cells: 1+ weak

B cells: 1+ weak

auto con: 1+ MF

anti-D: 1+ MFA

Weak D: 2+ MFA

DAT: 2+ MFA

Ok, I'm sorry that this is so long but i cannot ask the question without giving you this information. I know that this patient's ABO type is probably A,B, weak D.

I also know that this patient probably has an unexpected antibody because the DAT was positive. I know that we are seeing MFA on forward typing because the patient has 2 populations of blood cells in his system.

My question is why is the reverse typing done with the A1 and B cells positive? The O cells have no antibodies in them because it was packed cells which were given and the donor is always tested for bound antibodies if I am not mistaken. So, why the MFA with the A1 and B cells please explain. thanks in advance for any help

[Malcolm Needs ☆]

An excellent question!

I think that the key to the answer is the auto control being positive. This means that you cannot take any of your grouping results at face value (in particular, I would beg to differ with your conclusion that the patient has a Weak D phenotype, without performing the same tests on the pre-transfusion sample).

From the results with the ABO grouping reagents, I would suggest that the mixed-field reactions are due to the residual autologous red cells in his system, but that the mixed-field positive reactions in the D typing could well be due to the transfused red cells being coated with an, as yet, unidentified antibody. Further evidence for this comes from the positive DAT.

It is still possible that the reactions with the A1 and B cells in the reverse group could be as a result of the passively transfused residual plasma in the packed cells (remember, unless the red cells are so packed that they are almost solid, there will always be some plasma there - unless washed), but this is unlikely, unless one of the donors had phenomenally high-titre ABO antibodies, as the anti-A and anti-B in the units would be dissipated/diluted out by the circulatory fluid volume (and, I would guess that in such a case, volume expanders [crystalloids/colloids] would also have been transfused, diluting the antibodies still further).

"Some days later" is a little vague (not your fault - the fault of the person setting the question!), but primary immunisation usually takes a bit longer than "some days", so the production of a de novo antibody specificity is unlikely. The antibody is much more likely to be as a result of an anamnestic responce, and the thing to do here is to perform an elution on the red cells and investigate for the presence of an antibody in this eluate. It may just be useful to run a couple of group A and group B red cells against the eluate - but I doubt it!

I hope this helps a little bit, but I am certain others will have different, and very useful, opinions.

:idea::idea:

[David Saikin]

I think you have pretty well summed up the cogent possibilities Malcolm

[adiescast]

Malcolm has pretty much covered the reason for the typing discrepancy: Front type is mixed field from two cell populations (O and AB), back type is from the transfused donor units. The immediate spin D reactions don't really make sense. I would wash the cell suspension and repeat that. If the patient was Rh negative (as the initial results stated) and the units were Rh negative (unless they are mislabelled - God forbid!) and the D type still reacts at immediate spin after washing, then something else is going on there. Possibly a cold reactive antibody or Rouleaux. The weak D and DAT results are essentially running the same test twice at this point. Whatever is causing the one is also causing the other. You need an eluate to sort that out. I would recommend including A and B cells in the eluate testing. Having the screen results would be very helpful.

Any time you see mixed field reactions it is because there are multiple cell lines that are affected by the situation differently.

[Thandar Aye-zheng]

Fresh off school blood banker here. So, please bare with me if my technical terms are wrong.

Re: post tx mix field Intermediate Spin D+

Use 6% albumin as Rh Control to see if it is positive at immediate spin. If it is, this can be due to cold antibody coating the cells.

Re: Weak D+

Use Rh control when performing weak D?? If Rh control is positive, the positive result is due to antibodies coating on the red cells.

[galvania]

I would like to add a possibility for your mixed field result with the reverse grouping cells. Most commercial reverse grouping cells are pools. Therefore if your patient had a room-temperature active antibody (eg an anti-P1 or an anti-Lewis) then you could easily get a mixed field picture with your reverse cells.

For your weak positive reaction with anti-D, the question has to be asked, what type of anti-D reagent is this? If it has a high concentration of albumin, or the technique requires enzymes, then this result is a false positive due to the positive DAT. Just a question - what do you mean by MFA as opposed to MF?

[Malcolm Needs ☆]

Possibly mixed-field agglutination?????????????

[galvania]

As opposed to MF being mixed field without agglutination??????????

[Malcolm Needs ☆]

As opposed to MF being mixed field without agglutination??????????

Tee hee. Good point, but how many people do you hear saying or writing about the IAT test or worse still, the IAT technique? What on Earth do they think the "T" stands for????????????

[adiescast]

Trouble?

[Malcolm Needs ☆]

Almost correct!!!!!!!!!!!!!!!!!!!!!!!!!!!!