ABO discrepancy

[adiescast]

We have a new sickle cell patient that is giving us fits with the ABO type. The front type is AB, reacting 3+ with anti-A and 4+ with anti-B. The back type is B, reacting 3+ with the A1 cells and 0 with the B cells.

The A1 lectin and H lectin are both negative. The patient's plasma reacts 3+ with A2 cells. The screen is negative at immediate spin, so there is no reaction with type O cells.

When we typed the patient's cells with human anti-A (from a type B patient we had on hand with no identified antibodies), the cells were non-reactive.

Any ideas?

[SMW]

You mention this is a new sickle cell patient.....do you mean the patient is a neonate or "new-to-you" patient? If it's a "new-to-you" patient, with a diagnosis of sickle cell anemia, it's likely the patient has been transfused before so history from other facilities will be helpful. From the results you presented it sounds like the patient is a B(A) phenotype and the anti-A reagent you're using probably contains the MHO4 clone. Some group B individuals produce high levels of galactosyltransferase and attach some GalNAC which reacts with the MHO4 clone in some anti-A reagents. As you've already seen by your testing, the cells did not react with a human source anti-A. The patient should be considered group B for transfusion purposes. Fatalities have been reported when this phenomenon was not recongized and the patient was transfused with group AB blood.

Edited December 8, 2008 by SMW
originally asked about reactivity with A2 cells but re-read intial post and saw that was already reported

[marilynm]

First, which manufacturer's reagents were you using? I did not think the B [A] gave that strong of a reaction with Ortho's anti-A reagent, from what I remember. Also, were you using "washed' cells or if not did you repeat the ABO typing with washed cells? Did you test a control in parallel with your human anti-A from a B person to make sure it would pick up a "normal" group A2B? Can you get another manufacturer's Anti-A to test?

Marilynm

[marilynm]

PS I forgot to mention that some of the first examples of the B [A] phenomenon reported out of Kansas City were Black donors.

Marilynm

[rescyth]

i agree with mkmoulds...anomalous blood types does not usually give strong reactions. (If you haven't tried this)on the forward typing, try using washed cells then on the back typing try doing saline replacement...

-just my 2 cents

[Yanxia]

I agree with SMW.

[adiescast]

Sorry to take so long in returning...we were inspected (CAP)/assessed (AABB) last week.

To answer some of the questions posed:

The patient is a 5 year old with sickle cell disease. Her parents reported no previous transfusions. We used monoclonal anti-A from Immucor, which does not list the MHO4 as part of the clone. Washing the patient's cells did not change the reaction, nor did saline replacement of the back type. We did not detect any cold reactive antibody when we ran the screen at room temperature. Pre-warming the back type had no effect.

We did not have a normal A2B to test, but the human source anti-A did react with reagent A2 cells.

We called the patient a type B. Two type O units were transfused without reported incident.

[rescyth]

wow...so is this really a B(A) phenomenon?

[Yanxia]

I guess it is like B(A) phenotype, but the reaction is between the antibody in the reagent (of course not anti-A) and the antigen on the cells. Maybe you can test the patient's parents with this reagent. Because lots of antigen is inherited, and this kind of antigen is not popular in people.

[marilynm]

This is NOT a B[A], as the Immucor and Gamma-clone Anti-A reagents do NOT react with these types of cells, only the Ortho. What you have is probably some type of AsubgroupB with anti-A in the plasma. Some very weak A subgroups will react with commercial monoclonal anti-A but not single source human anti-A from a group B person. Their plasma can also react with both A1 and A2 cells. What you should do is type the RBCs of the parents of this child and I will bet you that one of them is a group A. And, I would love to see a sample on this child.

MarilynM