False Positives in Elutions?

[Seveets]

Hi all,

We had a tech fail her elution survey.

She had 4+ reactions (in gel) with all cells.

The correct answer was Anti-Fya which on repeat was found (the cells had hemolyzed but running a panel on this hemolsyte showed anti-Fya)

We use Immucor Gamma ELU_KIT II and the only false positive statement in the package insert in that the "use of low-ionic strength wash solution provided has been reported to give rise to the possibility of non-specific uptake of particularly strong antibody to antigen-negative red blood cells, leading to an eluate that is, in effect, falsely positive".

Does anybody know of any other reasons for this tech to get all positives??

Thanks,

[Mabel Adams]

Was the last wash negative?

[Seveets]

I believe it was but even if it wasn't the only antibody present (as show by the repeat testing of the now hemolyzed specimen) was anti-Fya.

[KathleenSL]

How well was the eluate spun? Was the tech careful during the transfer to a clean tube step? The eluate may have had residual cell (red cell, white cell, platelet) stroma in it. This can even interfer with tube testing results. We have included a second spin and second transfer step of the eluate before testing.

[Seveets]

As a follow-up, I believe the sample was not made up to the right pH

There are some at my facility who only add buffering until the first sign of a blue color or what they see as a permanent blue -- looks more yellow to me.

It happen again with what I call a yellowish eluate. The tech perform the survey and called 4+ results but to me they were of a strange mixed field variety.

I saw the color and added about two to three more drops to get to a beautiful light blue color. Retested and all but 3 of the positive results went away. Result was an anti-K

[OPUS104]

The pH is usually the culprit with us in Gel..... but on this last eluate from CAP (April/08) we had 1+ non-specific rxn on all of our cells except the antibody cells which were 4+ as usual for CAP sample. Requested new samples and retested yesterday. Same tech, same lots..... no extra rxns. We checked her pH on first eluate.....all ok. When we add the buffer we get a rxn of some sort sometimes. The eluate becomes hazy and you have to spin the formed particles out.... but this is very visible and I don't think anyone would miss it.