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Here is a weekend case: Patient's sample was A (forward) and backtyped as AB with provue. Tube testing was AB with forward and back typing, however it was only 1-2+ with anti-B. The weird thing was, it did not look like a mixed field. Even after 15 min. incubation at room temperature, backtyping did not change. At 4C, A1, B cell and autocontrol all came up positive. I only saw some A subgroups and A3 was mixed field. I would presume B3 would look the same. And so this case could be AB3. Is there a way to confirm it with genotyping? What is your opinion?

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There is a way of confirming it by genoty[ing, but it would cost the Earth for very little return.

I would like to know how old is the patient and what is the underlying pathology?

You have to remember that the the A, B and H antigens, in common with other carbohydrate-based red cell antigens, are not direct gene products, simply because only proteins can be direct gene products, whilst sugars cannot.  In the case of an AB individual, at least two different transferase enzymes are responsible for conferring either the N acetyl-D-galactoseamine residue, in the A antigen, or the D-galactose residue, in the case of the B antigen.  These two enzymes are in direct competition with one another as to which one "wins the race" to convert the H backbone to either A or B; sometimes the "A transferase" wins, and sometimes the "B transferase" wins.  In this case, it could be that the A-transferase is winning "hands down", and that the B-transferase is "whimping out a bit"!  Sorry, that last bit wasn't written exactly scientifically, but I hope you understand what I mean!

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18 hours ago, Malcolm Needs said:

There is a way of confirming it by genoty[ing, but it would cost the Earth for very little return.

I would like to know how old is the patient and what is the underlying pathology?

You have to remember that the the A, B and H antigens, in common with other carbohydrate-based red cell antigens, are not direct gene products, simply because only proteins can be direct gene products, whilst sugars cannot.  In the case of an AB individual, at least two different transferase enzymes are responsible for conferring either the N acetyl-D-galactoseamine residue, in the A antigen, or the D-galactose residue, in the case of the B antigen.  These two enzymes are in direct competition with one another as to which one "wins the race" to convert the H backbone to either A or B; sometimes the "A transferase" wins, and sometimes the "B transferase" wins.  In this case, it could be that the A-transferase is winning "hands down", and that the B-transferase is "whimping out a bit"!  Sorry, that last bit wasn't written exactly scientifically, but I hope you understand what I mean!

Thank you Maicolm! Patient is 46 years old. Dx: Lumbar foraminal stenosis

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On 7/23/2016 at 0:03 AM, WisKnow said:

Here is a weekend case: Patient's sample was A (forward) and backtyped as AB with provue. Tube testing was AB with forward and back typing, however it was only 1-2+ with anti-B. T

It's a bit unusual for the tube typing to be more "sensitive" than the automated (and I use that term loosely). May I presume that the anti-B used on the Provue and in the tube tests are formulated from different monoclonal cell lines?

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The genotype of this patient according to the results from a reference lab is A101/B101. A certain mutation makes his B subgroup so weak and variable, 

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5 hours ago, WisKnow said:

The genotype of this patient according to the results from a reference lab is A101/B101. A certain mutation makes his B subgroup so weak and variable, 

A101 and B101 are both the most common genes for the "A-transferase" and "B-transferase" respectively, meaning that there are no mutations at the molecular level of the genes.  It is still, therefore, much more likely that it is competitive inhibition between the two transferase enzymes that is causing the weak expression of the B antigen.

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1 hour ago, galvania said:

Could also be a mutation in the H-gene, meaning that there was less H to compete for.

Doubtful though Anna, as it would affect both the A and the B antigens equally, or nearly equally, in that case, whereas the expression of the A antigen appears to be almost normal.

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As neither anti-A and anti-B were detected by tube or gel in the patient's plasma and the patient's red cell genotype is AB, what is the appropriate blood group to select for transfusion?

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Until the genotype had been done, there was no definitive ABO type, and so group O should be given (there was never any suggestion that the patient was an Oh).  Once the genotype had been performed, and it was determined that the patient had the genotype A101/B101, then there is absolutely no problem in giving A1B.

51 minutes ago, Dansket said:

As neither anti-A and anti-B were detected by tube or gel in the patient's plasma and the patient's red cell genotype is AB, what is the appropriate blood group to select for transfusion?

 

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