Hope some expert can shed some light on this.  Patient history O Pos, done on 3 seperate samples in 2009.  Patient received 1 unit rbcs in 2009.  Today, patient is O Negative, done on 3 seperate samples, one of which was a witnessed draw by myself.  Patient denies Bone marrow or stem cell transplant - diagnosis is CML.   My best guess, based on Google, is a rare phenomenon seen in CML patients due to a mutation?  Of course, she was given O Neg rbcs.

Sounds like either impersonation (had you seen the patient yourself before?) or rare case, as you suggest above.

The other thing could be that the clones used in the anti-D have changed, and they no longer detect a particular mutant type.

33 minutes ago, Malcolm Needs said:

Sounds like either impersonation (had you seen the patient yourself before?) or rare case, as you suggest above.

That thought crossed my mind also - 86yr old woman - who knows?! 

Regarding the clones in Anti-D reagent, the results in 2009 were 3-4+, but I guess strength doesn't matter if a clone is either going to react or not react with this particular patient.  Interesting case, whatever it is!

Certainly is.  If you ever get to the bottom of it - and sometimes you just can't - let us know please.

We had a patient that seemingly converted from A Positive to A Negative.  We sent the patient to our reference lab and through whatever voodoo they do, discovered that she had proteins masking her D antigens.  I don't remember her specific disease process, and I don't think it was anti-D, but they reported that the patient was indeed A Positive.