Just curious how you would proceed in the following situation.

We had a patient whose antibody screen was negative and subsequently received 8 units PRBC. Now (10 days later), his antibody screen was positive and the id was a clear match of anti-K. The autocontrol was positive (1+) and, according to the technologist, the DAT was negative.

[The antibody screen and id were performed on MTS gel cards, and the DAT was performed using tube method]. My question is what would you do with the positive autocontrol? (The tech crossmatched units negative for K, but did no further investigation). Thanks.

~Steve

A tube DAT is less sensitive then a gel test, so repeat the DAT in the tube test (just patient cells in the gel column).

You should also make an eluate of the patient/donor cells, to look for the reason of the positive autocontrol. Beside the anti K there could also be an other antibody. When you find anti K (or something else) you should worn the MD for more red cell destruction.

Peter

Agree with Peter.

Just because there is a "free" anti-K in the plasma, it doesn't mean that there is not another covery antibody sensitising the red cells, which is not detectable in the plasma.

this patient is recently transfused so I would prepare an eluate and run it by Gel.

If this patient is not recently transfused, I would give K-,crossmatch compatible by gel ...that's it.

Definitely elute. We also report these as "delayed" transfusion reactions even if there are no clinical symptoms identified by the physician.

We find lots of weakly pos auto controls in gel that are neg by tube DAT. In general I am not sure I want the level of sensitivity that the gel DAT gives (especially in cord bloods). In this particular case with such recent transfusion, I too might want to do an elution, but our policy is not to do one unless the tube DAT is positive and the patient transfused in the prior 2 weeks. We have not seen any repurcussions from this policy although I agree with the others in the serological possibility of a new antibody being completely bound on the transfused cells. Gel probably picks up the free antibody in the plasma better (sooner) than in the days of albumin tube testing.

At my prior workplace we did elutions if the patient had been transfused in the prior 3 months and we basically never found anything more than we would have found using the 2 week rule which is what is recommended by our Red Cross reference lab.

This might qualify under the CDC transfusion reaction definitions as a "delayed serologic reaction", but unless there were some clinical evidence (even just lower Hgb than expected) I don't think they would classify it as a "delayed hemolytic transfusion reaction." (International disclaimer: In the US we put the quote marks outside the period whereas I understand the Brits would put them inside.)

(International disclaimer: In the US we put the quote marks outside the period whereas I understand the Brits would put them inside.)

Yeah, I never did understand that corruption...

If you get a pos auto but a neg DAT, in gel, you could try this; add patient cells to all wells of a 'monospec' card then add patient plasma to all wells and treat as an IAT (incubate, etc), see what happens

By 'monospec' do you mean IgG card? If I understand what you describe it is repeating the auto control in gel 6 times. Is that right? Maybe I am missing something because the only gel cards we have ever used are IgG.

I think what John means Mabel is by using the DAT card available from DiaMed/Bio-Rad in Europe, you perform an "auto" IAT in the DAT card, using the columns that contain monospecific anti-IgG, anti-IgA, anti-IgM, anti-C3c, anti-C3d and a negative control.

Is that correct John?

I think what John means Mabel is by using the DAT card available from DiaMed/Bio-Rad in Europe, you perform an "auto" IAT in the DAT card, using the columns that contain monospecific anti-IgG, anti-IgA, anti-IgM, anti-C3c, anti-C3d and a negative control.

Is that correct John?

That's what we did the last place I worked...

The IgG, IgA, etc., card is , indeed, the one I was referring to. We sometimes see the phenomenon where a pos auto, with a neg DAT, will give a positive resut (usually with the IgG reagent) if you do what I described.