What is causing this descrepancy? What further tests are needed?

[tuffgrrrrl]

An older man aged 62 has carcinoma of the colon and Proteus vulgaris has been isolated in his blood. He has a low hemoglobin and the M.D has decided to transfuse 2 units of packed cells and the crossmatch is ordered. Also 2 years prior he had some G.I bleeding and required 4 units of group A Rh+ red cells and there was no problem at that time. Current grouping results are:

Anti-A 4+

Anti-B 1+

A1 cells neg

B cells 4+

Sal auto neg

anti-D 3+

6% alb neg

What is causing this discrepancy and whatblood group does he need and shuld he recieve washed rbcs, whole blood or packed rbs?

[LaraT23]

Ok this is text book acquired B. With Carcinoma of the colon, the patient's red cells acquire a B type antigen on the surface. It is not a real B antigen so using acidified reagent should do the trick. The B antigen should go away. Also, check to see what reagents you are using, the clone types you have react to the acquired "fake" B antigen and maybe you should keep more than one supplier or switch if need be. Ortho uses clones that are not known for cross reacting with acquired B.

He will need A pos red cells and no washing is necessary. As far as the whole blood issue, no one uses that anymore that has a choice not to!

Edited November 10, 2010 by LaraT23
typo, sheesh

[Malcolm Needs ☆]

Excellent answer Lara.

If you want to learn more about this phenomenon, I would thoroughly recommend reading Geoff Daniels on the subject in Human Blood Groups, 2nd edition, 2002, Blackwell Science, Chapter 2, pages 48 to 50.

By the way, everyone, Geoff is bringing out a 3rd edition, which is due out in October 2012. I, for one, will be putting my name down for a copy as a matter of urgency!

:excited::excited:

[KKidd]

I have seen an acquired B only once in my career. It certainly reminds us how important a patient history is. Finally one of your case studies that I understood.

Malcolm, you certainly manage to stretch my brain with most of these case studies. Fortunately, it is still rather resilient(most of the time)

Karen

:clap::sing:

[dcubed]

I always seem to come in to late! I actually had a pretty good idea what was going on here. Interesting case.

[Dr. Pepper]

We had an aquired B several years ago, also with cancer of the colon. What was kind of neat for us as blood bankers (not for the patient, alas, who passed away a few months later) was that he started off typing as a normal group B, but we got to see gradually increasing reactivity with anti-B as the days passed and his condition worsened.

If you wanted to beat the problem into the ground, other things to check out would be that the patient's anti-B will react with normal B cells but not his own aquired B cells. If a secretor, he will secrete A and H substance but not B substance.

[L106]

We had an aquired B several years ago, also with cancer of the colon. What was kind of neat for us as blood bankers (not for the patient, alas, who passed away a few months later) was that he started off typing as a normal group B, but we got to see gradually increasing reactivity with anti-B as the days passed and his condition worsened.

If you wanted to beat the problem into the ground, other things to check out would be that the patient's anti-B will react with normal B cells but not his own aquired B cells. If a secretor, he will secrete A and H substance but not B substance.

I think you meant to say that the patient started out as a normal Group A individual, right?

[Dr. Pepper]

Oops, how embarassing. You can see how red my face is. At least this shows that someone actually reads these posts.

I had an exercise that my students used for years that showed compatability frequencies for the various antibodies. The top of the list stated that if you had anti-D you were compatible with 100% of Rh positive donors and 0% of Rh negatives. I finally noticed but several classes of students didn't.

[L106]

Been there, done that!

[rravkin@aol.com]

Ok this is text book acquired B. With Carcinoma of the colon, the patient's red cells acquire a B type antigen on the surface. It is not a real B antigen so using acidified reagent should do the trick. The B antigen should go away. Also, check to see what reagents you are using, the clone types you have react to the acquired "fake" B antigen and maybe you should keep more than one supplier or switch if need be. Ortho uses clones that are not known for cross reacting with acquired B.

He will need A pos red cells and no washing is necessary. As far as the whole blood issue, no one uses that anymore that has a choice not to!

Lara,

Are there any alternative procedures to resolving this discrepency outside of the use of acidified reagent?

[cmiller]

We had a case of acquired B a few months ago, also in a cancer patient in a nursing home. We'd typed & crossmatched this patient many, many times as group A, Rh+. We detected the acquired B using manual Gel and had the following reactions:

Anti-A: 4+

Anti-B: 1+

Anti-D: 4+

Ctrl: 0

A1 Cells: 0

BCells: 4+

When we repeated testing using tube reagents, the reaction with Anti-B was negative and all other reactions were as expected for group A, Rh+ individual.

Very cool to actually see this.

I just gave all our techs some case studies on A and AB subgroups with Anti-A1 and I also included this case on acquired B. I think the cases really made them think about things we don't see very often.

They actually seemed to enjoy it - much to their surprise!

[LaraT23]

Well the best way to avoid it is to keep in stock a reagent that does not use the ES-4 clone. The manufacturer insert should tell you which clone they use. Since this all was discovered, most manufacturers do not use that clone any more anyway, so there are good odds we should not see this as much anymore. The bacteria shave off the terminal acetyl group attached to the last galatose away from the cell membrane, and they don't get all of them, so the "fake" B reaction is usually much weaker than the expected 4+ we would see in a true AB or B individual.

[profbaud]

One other trick for solving this is to use the patient's serum and the patient's red cells. The Anti-B in the patient's plasma will not agglutinate the acquired B cells since they are really group A cells with a modification to the A sugar made by an enzyme from the Gram negative bacteria.

[Malcolm Needs ☆]

Good point profbaud.

[Mary Ann]

The patient is A pos with an acquired B due to the bacteria,thanks for sharing this.