These are, for want of a better way of putting it, antigens that are expressed on IgG molecules.

Gm stands for Gamma marker and Km stands for Kappa marker.

An individual will have their own Gm and Km types, and all of their antibody molecules will express these types.  However, other individuals will (probably) express different Gm and Km types and, of course, anti-D immunoglobulin is made from a pool of human-derived anti-D.  Therefore, if the anti-D in the circulation has multiple Gm and Km types, it is almost certainly derived from anti-D immunoglobulin.  On the other hand, if the anti-D has the same type as the patient, it is probably an allo-anti-D.  That having been said, however, this has never been proven (as far as I know), and, even if there is a "soup" of Gm and Km types in the circulation, this does NOT disprove the presence of a weak allo-anti-D.  This is why I put this forward as a possible way of serological typing, but I also did say that it is not 100% reliable.

On 12/6/2019 at 7:49 AM, jnadeau said:

Thank you ALL for your insightful posts - my student is a little overwhelmed with some of the replies (and might be sorry she asked) but she's very sharp and also appreciates your expertise - it's led to some thoughtful discussions here.  Since we would have a negative antibody screen performed shortly before they would give a RhIG shot and since we "rule out" some antibodies without respect to dosage when performing an antibody screen I think we'll continue with the abbreviated panel in these instances.  Happy Holidays to you all. 

 

I tell my techs that the abbreviated panel performed when RhIG was recently given is like running an antibody screen using all RhNeg cells.  It is not designed to identify an antibody, rather to detect the presence of clinically significant antibodies.  In reality, every patient we get a negative antibody screen result on has not been subject to strict "rule outs", particularly if you are using a 2 cell screen.