Funky anti-M or ?????

[Mabel Adams]

MTS gel 2 cell screen both cells positive with a MF, rouleaux or cold antibody looking reactivity. MTS panel shows same reactivity in all M+ cell but negative in the 2 M- cells (weaker with some hetero cells); auto control is negative. (These reactions are hard to grade but there is a big line at the top, a cell button in the bottom and not a lot of agglutinates in between. The sample was respun before the panel testing so it is not just topline.)

Testing in tube at IS is 1+ with 3 MM cells and neg with 3 NN cells. These tubes were carried through AHG (30 minutes, no additive) and appeared to have rouleaux at 37 which disappeared with saline replacement and the IgG phase was neg with adequate Coombs control cell rxs. A 3 cell tube screen was run (saline, 30 min) that showed 1+ at IS with the MM cell and micro+ with the 2 NN cells (I wouldn't have read these microscopically but this tech did). Again, rouleaux at 37 that disappeared with saline replacement and neg with IgG. The patient's cells antigen type 3+ with anti-M reagent and she has no record of transfusion that we know of. Two units were crossmatched in MTS gel and were both compatible--one was M+ and one M-. Taking all interpretations and thank you very much.

[Malcolm Needs ☆]

Sounds like a "naturally-occurring" anti-M to me, but not a "normal" one.

[galvania]

I agree that it doesn't sound normal. In my experience, when you have what looks like a double population in the antibody screen, unless you are using pooled cells, then you either have fibrin or you have a reaction that is not normal, but patient-related rather than cells-related. I have frequently seen this happen in the presence of an enzyme anti-E or-Cw. It is sometimes IgM and sometimes not - can be negative in saline at RT/37°C

[David Saikin]

In gel what you describe is a classic "cold" ab reaction (or fibrin in your specimen) . . . sounds like an anti-M to me too.

[SMILLER]

Or more likely a cold that mimics and anti-M. These are quite common. Since the patient is M positive, you only have to do a coombs crossmatch to find compatible blood for transfusion.

Scott

[Joanne P. Scannell]

I agree ... it's a cold antibody with the specificity Anti-M (all cold antibodies have specificities, most we just report out 'Cold Antibody of Undetermined Specificity' ... really, they are clinically insignficant unless you are going hypothermic during surgery or such). Your reactions (Mixed Cell) in MTS is classic cold agglutinin (refer to the interpretation guide) ... we see Anti-M like this a lot.

Also, MTS is more acidic than tube testing. If you are old enough to remember, we used to acidify serum to enhance Anti-M if we suspected that antibody. So, by using this system that is somewhat acidic, we expect (and do!) see a lot more Anti-M than before.

Rouleaux is often seen with cold agglutinins ... they are large molecules (IgM) and increased production can skew the Total Protein/Albumin ratio enough to cause rouleaux. So, be not surprised at that observation at 37oC (the proteins are still there even though the antigen-antibody reaction is not occurring at that temperature).

Also, be not surprised the patient is typing M-Pos with your 'Anti-M' reagent (and with a negative auto). I venture to say your patient is really Mg-Pos. (There is something about the M antigens that cross react, so antigen typing with a reagent is not as pure as other typings are. This is very common ... so common that I don't recommend my staff type the patient with Anti-M 'to validate the antibody ID' because it's more confusing to a novice tech than it is worth.)

Transfusion:

Establish if this Anti-M reacts at 37C. Prewarm testing will help determine that.

- If reactive only at Room Temp: Our policy is that if the patient has a cold agglutinin, we recommend a blood warmer. This is only precaution and makes everyone feel better about transfusion 'incompatible' RBCs. (I.S. will be incompatible unless you go through absorptions ... but why bother with all that?) With a cold agglutinin that reacts with only some donors (like Anti-M), we just crossmatch (I.S) and issue the compatible units first. Of course, if the OR is planning hypothermia, it becomes a clinically significant antibody ...

- If reactive at 37C it is potentially clinically significant ... go by your current policies for giving antigen-negative/extended crossmatched RBCs when the patient is producing a clinically significant antibody.

Sorry if I rambled on this ... we see these a lot now that we are using MTS.

[Mabel Adams]

This is all great input. How do you explain the gel crossmatch with M+ cells that is compatible? Maybe diluent 2 is not so acidified as the diluent for the pre-diluted cells? Or maybe that donor is also Mg pos but M neg? I see that Mg is a very low frequency antigen.

[Malcolm Needs ☆]

Well Mabel, one answer to this is that the red cells used for screening and antibody identification are conserved in a solution that keeps the antigens at optimal expression, irrespective of their ability to carry/transfer oxygen, whereas the red cells in a unit of blood are conserved in a solution that keeps therrespective of there oxygen carrying capacity/oxygen transferrability (is that a word? if it is, I BET I have mis-spelt it!) irrespective of the expression of the antigens. It maybe, therefore, that the M antigen on the red cells of the cross-matched units had been degraded.

I'm not saying that this really is the answer, but it may be a contributary factor.

[Joanne P. Scannell]

Yep ... maybe that donor is not homozygous for M.

[rravkin@aol.com]

Mabel, have you considered drawing a second specimen, at a later time? Have you considered performing full crossmatch in tube and testing all phases?