anti-M

[Ab0301]

Hi

In our lab we use ortho technology. We see an extraordinary number of patients with anti-M. In the last few weeks we have had a few patients with a clear anti-M reactive by IAT at 37oC. These patients are positive for the M antigen and DAT negative, no history of transfusion. Can anyone give advice? Should these patients be getting M- red cells?

[Yanxia]

DAT neg , pos M antigen and anti-M antibodies, that is intersting, what about the auto-control. Just my guess, because the ortho tech is very sensitive,so weak antibodies can be tested, but the patient  has anti-M on his own cells , but it is too weak to be detectd by DAT test , maybe autocontrol  and elution can tell us something.

[clumbert]

Are many of your patients on renal dialysis?  Do you test serum or plasma?

Do you test manually, in y gel, or with LISS?  Do you include an immediate spin in your testing?

Anti M is usually considered not significant but sometimes, it attaches on direct agglutination and doesn't elute off whith washing but if the antibody reacts under strict pre-warm conditions, it should probably be treated as significant.

We experience frequent Anti-M in dialysis patients and found it was happening only after dialysis.

We learned it was because the clinic sterilized their dialysis machines with a dilute formaldehide solution.

 

Chuck

[SMILLER]

Someone check me here, but one of the reasons we do not worry about M so much is that cold insignificant antibodies, including some autos, often mimic anti-M.

 

Having said that, if a strict pre-warm does not get rid of it at 37 (or coombs), I would say you are stuck with a possible anti-M IgG.  It's odd you turn up so many of these though.

 

Scott

[R1R2]

Be careful with the reagent anti Ms out there.   Some only require a RT incubation with no centrifugation before reading.   I have found that centrifugation may cause false positives.   Read those package inserts!

Edited April 10, 2015 by R1R2

[Malcolm Needs ☆]

Also be aware that, in addition to the problem of anti-M sensitising red cells in a very short time frame, but taking longer to elute off, as stated by Chuck above, the columns are slightly acidic, and the M/anti-M reaction just loves acidic conditions - some as low as pH4.

[David Saikin]

I too have seen a few anti-M's with M+ pts recently.  These were only reactive with the homozygous expression of M and the pt's also had an underlying cold agglutinin (specificity undetermined).  These M's were not clinically significant.  Tube testing did not demonstrate any alloimmunizations . . . we transfused prewarmed, IgG xm compatible rbcs.  My Medical Director is comfortable with transfusing without M typing as long as we can document there is no anti-M activity at 37C/ahg phase.

 

I agree, watch out - Ortho's anti-M should not be centrifuged.