Questions about a potential A subgroup

[AmyL86]

Hi, think this is my first post here. My name is Amy, just to share a tidbit with everyone.. 

 

I had a patient today that typed as such:

 

Forward type:

Anti-A = 2+

Anti-B = 4+

Anti-D = 4+

 

Reverse type:

Acell = 0

Bcell = 0

 

Anti-A1 = 0

 

87 y/o male, oncology patient. 

 

I was reviewing reports for the BB Supervisor, when I saw the weak Anti-A in forward, I investigated and got the aforementioned results.

The overnight tech released A+ blood on this patient, but no symptoms of transfusion reaction.

I notified my pathologist and switched the patient to O+ in light of the absence of A1 antigens.

 

my question:

I am surprised to see that the A cell in the reverse type is coming up negative. In my texbook, type discrepancies such as this are accompanied by the presence of anti-A1 in the patient's plasma. Here, I don't have a demostrable Anti-A1 and I am wondering if the antibody is naturally occuring, and in what frequency?

 

 

 

 

[rravkin@aol.com]

Amy, have you tried any reaction enhancements for the forward Anti-A and the reverse A1?

[galvania]

Dear Amy

There are two possibilities here. 

 1.  This patient is an A2B (or a weaker subgroup of A - maybe an A3) without an anti-A1.  Not all patients with weak A subgroups have an anti-A1.  About 20% of A2B individuals would be expected to have an anti-A1 - that still leaves the majority without.  The anti-A1 is naturally occurring.

2a.  If the patient has a 'haematological' cancer, it is well-known that the ABO antigens can be affected: They often return to full strength when the patient is in remission

2b.  If the patient has a stomach or bowel cancer, he may be producing excess soluble A substance which may be blocking the reaction between the A antigen and the anti-A.

As this patient is a group AB you should not really be giving group O.  If you don't like the idea of transfusing AB then group B would be the group of choice - but I don't see any problem with issuing AB for this patient.

[Mabel Adams]

I'm with you, Anna.  This looks like a normal A2B patient to me.  My husband, daughter and mother-in-law are all A2 and none has anti-A1.  The rate of having anti-A1 is higher in A2B than in A2 people but, as you point out, those with the antibody are the minority.

[EDibble]

I am also an A2 with no anti A1. It is so much fun to be able to do complete antigen workups on yourself when in school.

[John C. Staley]

Don't for get that it is not unusual for antigen expression to diminish with age.  Personally, considering the patient's age and diagnosis, I would not be to quick to jump on the A2B band wagon. 

[rravkin@aol.com]

Hi John, I would agree that given the patient's age the A1 antigen may very well be weaken however if we are seeing Anti-A reaction at 2+ shouldn't we expect some reactivity with Anti-A1 lectin if the patient indeed has an A1 antigen? I am not sure which test if either is more sensitive, or if sensitivity is even an issue.

[John C. Staley]

I missed the results of the Anti-A1 lectin testing. I guess I didn't recognize it as such with out the "lectin" specification, but I should have. You are correct, I would expect it to be positive if the patient was an A1, at least as positive as the original A1 testing. So now I'm more ready to jump on the A2B bandwagon. Move over.

[Mabel Adams]

Hmm. Weakening A antigen with age.  Maybe that is why I now type as an A2 with anti-A1 lectin when in my twenties I typed several times as A intermediate.  Naah.  I'm going with different reactivity of the lectin.

[John C. Staley]

Hmm. Weakening A antigen with age.  Maybe that is why I now type as an A2 with anti-A1 lectin when in my twenties I typed several times as A intermediate.  Naah.  I'm going with different reactivity of the lectin.

 

Besides, you aren't that old yet Mabel.  Maybe someday but not today.