Hi,

Is mixed field a valid result for an antibody screen done by gel method? If so, under what circumstances would that be reported? I found an older thread regarding the degradation of antigens on stored reagent cells yielding such a reaction, but these were relatively fresh screening cells.

Thanks,

Amelia

Ortho states that, unless you are using pooled reagent red blood cells, a mixed field reaction is not possible. Yet, for all intents and purposes, we see them occasionally in patients with protein issues and some direct agglutinating antibodies such as cold agglutinins. We consider these reactions inconclusive and go on to investigate the possible causes, which are not likely to be significant IgG antibodies.

When we get this, we repeat with a different set of screening cells; it usually goes away. If not, we consider this an invalid result and go to another method (tube PEG).

mf reactions in gel - either a cold agglutinin, fibrin in your specimen or your pipeting technique could be better (if you get a lot of cells in the column instead of the rx chamber).

I have never seen a REAL mixed field reaction on gel. It is always junk. Usually a cold or rouloux. IT can also be too many plts or too much plasma protein or idiopathic junk. I would never call something mixed field without looking under a microscope on tube. At least not with technology now available to me.

What we do with 'mixed field' gel reactions (top and bottom cell populations): Repeat by tube and stay with tube if workup needed. Probably 70% are colds showing at IS. Most of these do not show any specificity though Anti M will sometimes present this way.

I have seen anti-E look this way in gel. Of course, it is probably one that has an IgM component. Someone once told me you can also see this effect with an antibody that is a "poor fit" for the antigen--like you might see when it is first being produced and fewer B cell clones have been recruited to make antibody. Otherwise, all that is mentioned above is more common.

What we do with 'mixed field' gel reactions (top and bottom cell populations): Repeat by tube and stay with tube if workup needed. Probably 70% are colds showing at IS. Most of these do not show any specificity though Anti M will sometimes present this way.

I should have made clear that REAL allo antibodies can and do hide out amongst this stuff which is why we go to tube and follow regular tube identification methods for any antibodies found. Like Mabel I have found allo antibodies on the tube in a distinct pattern once the gel interferences were removed. But once we go to tube screen any further antibody identification continues by tube.

we see mf in gel wil very strong rouleaux and cold antibody.

I have seen very nice mix field in Gel with Anti-Lua......cell button at bottom and cells throught column....2+Mf

This is characteristic of most Lutheran antibodies. They tend to give reactions that look like 2+ positive clumps of agglutination in a sea of negative agglutination (bit like an A3 reaction).