Gel vs Tube discrepancy

[Liz]

A blood sample from a patient with DIC and post dialysis gave AB on the tube method and O on the gel method. The patient is known to be O. Washing the cells did not change the tube results.

A sample a few hours later gave O on both methods.

What happened?

Thanks

Liz

[David Saikin]

How strong were your reactions with anti-A and Anti-B? Are you certain the blood was obtained from the correct patient? Was there a positive DAT?

[bloodsucker]

:)have you done back typing? since it is more accurate to determine the blood type by knowing the anti-A, anti-B reaction.:-)

[John C. Staley]

:)have you done back typing? since it is more accurate to determine the blood type by knowing the anti-A, anti-B reaction.:-)

I'm curious, where did you come up with back typing being more accurate than forward typing?

[Liz]

How strong were your reactions with anti-A and Anti-B? Are you certain the blood was obtained from the correct patient? Was there a positive DAT?

The tube and slide method were 3+ with anti-A and Anti-B.

We did ask for new samples and they were all O. But even with a wrong sample I was still wondering why the same sample gives such different results on 2 different methods.

We did the reverse on the gel and there was no discrepancy on forward and reverse there.

We did not do DAT (I shall try and preform that now), and there was no serum left for reverse on tube method.

Thank you

Liz

[AMcCord]

Was the first sample a line draw? Did you have one sample tube that was used for both tests? Could there have been a contaminate present in the sample that gave you the AB results?

[Liz]

Was the first sample a line draw? Did you have one sample tube that was used for both tests? Could there have been a contaminate present in the sample that gave you the AB results?

I shall ask if it was a line draw.

Yes, the same tube sample gave the different results. That is what perplexes me. It was done several times by different technologists and the tube was always AB and the gel would be O.

Thank you

[normam]

The fact that Gel method gave a more accurate blood type, it's more likely that something is coating the cells giving the discrepant clumping. If it was a line draw and compromising the test, you should try washing the cells several times with warm saline then forward type by tube method. Back typing is not a confirmatory test for blood typing and as a general rule we always go with forward typing. the discrepancy is generally showing in back typing thats why we have to resolve when a discrepancy is observed in reverse typing before we can accept the forward typing.

[galvania]

Idea no. 1....Are you using monoclonal reagents for both? I presume the gel is with monoclonal antibodies. If you are using polyclonal (human) antisera for the tube test, then you could well be dealing with polyagglutination.

Idea no. 2....I presume you are using saline or LISS to make the cell suspension for the tube test and a proprietary diluent for the gel test. The composition of the two would be different. It is possible that there was a reaction between the chemicals in the diluent used in the tube technique and the sample that was somehow altered slightly due to the dialysis. In which case your reagent control would have also been positive.....

Idea no. 3...I don't think a positive DAT would interfere with the ABO group unless it was due to strong cold agglutinins (in which case the gel would also have gioven 'false' positive results) or you you were using a suspension solution with really strong potentiators fopr the tube technique only. Again, your reagent control would have been positive...

[Liz]

Thank you all for your thoughts. Indeed these are different reagents, and that explains it.

We did wash the cells but we still got AB on the tube method.

So it is due to the different reagents and how the cells reacted to that, given this is not a regular patient. Once the DIC was resolved, tube and gel both gave 0 pos.

Thank you!

[Mabel Adams]

Did you have a positive D control in tube?

[NANCY AUGENSTEIN]

A blood sample from a patient with DIC and post dialysis gave AB on the tube method and O on the gel method. The patient is known to be O. Washing the cells did not change the tube results.

A sample a few hours later gave O on both methods.

What happened?

Thanks

Liz

I have had a few discrepancies between gel and tube. The Provue probe will sample blood from the very bottom of the tube. The blood at the bottom tends to be the freshest or heavier. So if the Rh pos patient was transfused with Rh neg recently you get the dual population of Rh or it will type totally Rh neg if there was a massive transfusion. Same thing would happen if the patient had received alot of another type. Tube testing is a big mixture of cells.

Also I have seen a difference between the Ortho reagent on the Provue and Immucor reagent used with tube testing.

[Liz]

Did you have a positive D control in tube?

No, the control was negative.

[David Saikin]

Nancy

I have to disagree with your statement that the freshest red cells are at the bottom of the tube. Retics are always at the top of a spun tube - this is why and how we can Ag type an individual who has been recently transfused, i.e., by removing the top 4mm of a spun hct tube, we should only get the pt's cells, not the transfused (older?) ones.

[rescyth]

i agree on david on where is where.

Edited April 12, 2009 by rescyth

[marilynm]

Just a few comments on the above case. There are NO commercial reagents licensed in the US that are human source; they are all monoclonal. Secondly, I would like to know how strong the reactions in the tube were with the Anti-A and Anti-B reagents? Were they also Ortho reagents or from a different manufacturer? Also, did the cells give any negative reactions in the tube with any other reagent, like a monoclonal control for the Rh (in the case of the ImmucorGamma reagents there is a Clone Control that is a dilutent used in the Anti-D reagent). Washing the cells should have eliminated the reactions in the tube unless the cells spontaneously agglutinate in the diluents used for the reagents (like due to pH). I assume the screening and autologous control were negative?

Sorry for the questions. Marilyn M

[Liz]

Just a few comments on the above case. There are NO commercial reagents licensed in the US that are human source; they are all monoclonal. Secondly, I would like to know how strong the reactions in the tube were with the Anti-A and Anti-B reagents? Were they also Ortho reagents or from a different manufacturer? Also, did the cells give any negative reactions in the tube with any other reagent, like a monoclonal control for the Rh (in the case of the ImmucorGamma reagents there is a Clone Control that is a dilutent used in the Anti-D reagent). Washing the cells should have eliminated the reactions in the tube unless the cells spontaneously agglutinate in the diluents used for the reagents (like due to pH). I assume the screening and autologous control were negative?

Sorry for the questions. Marilyn M

Thank you for the questions, it helps to clarify the case.

The reactions in the tube with the Anti-A and Anti-B reagents were 3+.

The reagents are from Ortho

We do not use any other reagent for the tube method.

The screening and autologous control were negative.

The washed cells gave the same positive results with the anti-A and anti-B.

Thank you.

Edited April 20, 2009 by Liz
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