This may sound a very interesting case. An old male patient was admitted to our hospital for elective spine surgery. His blood type is AB Rh Positive. He was requested for a unit of platelet pheresis and got transfused a day before his operation. After this, 1 PRBC was also transfused. Before the RBC unit was completely given, the floor called for possible transfusion reaction study. Post transfusion reaction was positive with poly, IgG and C3 but not with saline control. Eluate was negative with all cells tested including A1 and B cells. Pre transfusion sample was DAT negative. Since patient had anaphylactic shock, sample was sent to a reference lab for further investigation. The ref lab tested the eluate with A, B, AB and O donors. It turned out that his eluate was positive only with A, B and AB but not with O donors. Isn't this weird? Eluate was negative with cells tested including A1 and B cells but tested positive with donors:  1+ with A and B donors, 3+ with AB donors and clearly negative with O donors. Have you encountered a case like this?

DO I presume that both the unit of platelets and the unit were group AB?

The PLT was A but the RBC was AB

We're all all of the tests of the eluate performed by IAT, including tests against reagent A1 and B cells?

Well. the plasma from the platelets would explain the anti-B, but what about the anti-A?  I'll have a think.

Could be anti-A1, from the platelet plasma (from A2 donor, with anti-A1), but why no reaction with reagent A1 & B cells (if all tests done by IAT)?

Could be the antibody is directed against an element of the plastic bags that are used for the blood and blood components, but are not used for the reagent red cells.  It would not be the first time this has been reported, but then, why not the group O units of blood and blood components?

10 hours ago, John Eggington said:

We're all all of the tests of the eluate performed by IAT, including tests against reagent A1 and B cells?

Yes, all were performed using eluate PEG-AHG.

Did the patient receive IVIG or Winrho?  We had a patient that received a passive Anti-A that was unexplained until it was found that patient had received this product while in visit prior to receiving some blood products.

1 hour ago, yeleng22 said:

Did the patient receive IVIG or Winrho?  We had a patient that received a passive Anti-A that was unexplained until it was found that patient had received this product while in visit prior to receiving some blood products.

No, he did not receive IVIG. That was the first possiblity that we looked into. But there's one thing that we noticed. The washed A, B and AB donor cells were stronger with patient's eluate than with the unwashed. I already mentioned that eluate was negative with both washed and unwashed O donor cells, also negative with unwashed A and B cells. So we will try to wash the A1 and B reagents cells and see what we'll get. We have a feeling that the reagent cells express antigens weakly and by washing may uncover more antigen binding sites.

13 hours ago, WisKnow said:

No, he did not receive IVIG. That was the first possiblity that we looked into. But there's one thing that we noticed. The washed A, B and AB donor cells were stronger with patient's eluate than with the unwashed. I already mentioned that eluate was negative with both washed and unwashed O donor cells, also negative with unwashed A and B cells. So we will try to wash the A1 and B reagents cells and see what we'll get. We have a feeling that the reagent cells express antigens weakly and by washing may uncover more antigen binding sites.

Reagent red cells certainly do not "express antigens weakly". There is no way a commercial entity would risk distributing a product that might give rise to customer complaints - the regulating bodies (the FDA in the USA) would be all over those issues. There may be some weakening of antigen strength over the life of commercial red cell products, but this weakening would probably only be noticed with a borderline, wishy-washy antibody - perhaps you have stumbled upon such a beast.

Commercial reverse cells (A1, A2, B, O) are washed extensively before preparation of the products. Additional washing will not "uncover more antigen sites". At most, washing (with saline) will remove the commercial red cell diluent/preservative and change the chemical environment of the test system. This change may indirectly enhance or suppress reactivity of some antibodies.

If you are using unwashed cells in ABO tests, remember that ABO substance will also be in the plasma/serum and may neutralize an antibody before it has a chance to bind to the red cells. In such a case, washing will definitely enhance reactivity.

If I understand it correctly, the lab tested an eluate that they had made against reagent A1 and B cells and it was negative; and the reference cetre tested the donor cells - with an eluate that they had made or with the eluate that the lab had made?  I suspect they made their own eluate....Could be down to a difference in method for the elution.  Also - from the same sample or a different sample? 

It seems like we are seeing more strange antibodies these days.  We had a known B+ patient that was only compatible with group O red cells recently.  ABS was negative.  RG as an O.

3 hours ago, macarton said:

It seems like we are seeing more strange antibodies these days.  We had a known B+ patient that was only compatible with group O red cells recently.  ABS was negative.  RG as an O.

Interesting, those of us doing electronic crossmatch would never see this.

We ended up reporting it as non specific reactivity. Thank you guys!