Hello everyone.  

We had a new patient the other day that typed as a B on the Vision but when doing the 2nd ABO confirmation (our hospital requires a 2nd sample), there was a discrepancy.   these are the results that the tech who was working on it got.

anti-A  2+     Anti-B  4+    A1C  4+    BC  0    A2C  1+

She interpreted the ABO/Rh as AB but put the patient on group O cells only and plasma restriction.  she also put a note saying that it is a probable B(A). 

can anyone please give me some information about this type of discrepancy?

What is causing the discrepancy and what can be done to resolve it?

Was it correct to interpret the ABO/Rh as AB?

if the patient is a B(A) phenotype, what type RBCs and plasma would you give?

 

 

 

 

It is important to remember that the A, B and H antigens are not direct gene products, but are their as the result of the action of specific transferase enzymes.  In the case of a group AB individual, the N-acetyl-D-galactosaminyl transferase (the A transferase) "competes" against the D-galatose transferase (the B transferase), and it is not unusual to come across a case where "one transferase has beaten the other".  This results in an apparent weakened A or B antigen, and this could be the answer in this case.  It could also be, of course, that there is a "genuine" weak expression of the A antigen, due to the patient inheriting an A² gene (or other weak A gene).

This could be checked by adsorption and elution tests with an anti-A.

The reaction with the A₁ reverse grouping cells could be due to an anti-A₁ in the plasma, but this would not account for the reaction with the A₂ reverse grouping cells.  This latter reaction could be due to a "cold" auto-antibody, such as auto-anti-H, auto-anti-HI or auto-anti-I, or to a "cold" reacting allo-antibody, such as anti-M or anti-P1, where the corresponding antigen is not being expressed on the B reverse grouping cells.  This, of course, would all have to be proven with appropriately typed reagent red cells.

Depending upon the anti-A reagent you are using, but I assume that you are using a monoclonal reagent, I would be happy myself to call this an AB, and not waste my group O stocks unnecessarily.

Lastly, as far as plasma is concerned, I would try to give group AB, but also wouldn't hesitate to give either A (preferably) or group B, unless the patient is of small stature, in which case I would definitely go for AB.

Or, more mundanely, the reaction in the anti-A could be down to carry over.  When working with gel, if there is condensation in the reaction chamber, or even worse, directly under the aluminium, this can be carried over when pipetting or when removing the aluminium.  As the antiserum is so strong this can lead to false positive reactions - rarely a 4+.  Is it too late to see a picture of the pipetted card?

Hi, We recently also had a B (A) phenotype detected by the Ortho reagents.  Our reactions were similar to yours. We are fortunate to have a R&D Rh gentoyping facility at our Reference Lab here in Brisbane, Australia who confirmed the B (A) phenotype. I confirmed with Ortho they are using the clone which detects this.  We transfuse Group B where possible. 

49 minutes ago, Kellimq said:

Hi, We recently also had a B (A) phenotype detected by the Ortho reagents.  Our reactions were similar to yours. We are fortunate to have a R&D Rh gentoyping facility at our Reference Lab here in Brisbane, Australia who confirmed the B (A) phenotype. I confirmed with Ortho they are using the clone which detects this.  We transfuse Group B where possible. 

While I admire your tenacity in following up your case Kellimq, unless your R&D Rh genotyping facility is well-practiced in ABO genotyping ( and I am NOT saying that they are not), you should keep in mind that ABO genotyping is notorious for predicting ABO phenotypes that do not necessarily match the genotype (see Daniels G.  Human Blood Groups.  3rd edition, 2013.  Wiley-Blackwell, p25, Section 2.3.2.6 Predicting ABO phenotype from DNA testing.).  Certainly, in the UK, our Histocompatibility and Immunogenetics Laboratories, who used to perform ABO gentyping when performing the tests for renal transplants have been banned from so doing, and now have to use good old-fashioned serological techniques, are one unfortunate episode.

Edited November 22, 20177 yr by Malcolm Needs