Malcolm, that is fascinating to know why they change their Lewis types.  We don't keep Lewis antisera.  I just realized that the titer in 2018 was for anti-D, probably to figure out if it was too high to be due to RhIG (titer was 1).  So, I will quit casting aspersions by suggesting they were ordering Lewis titers.

I'm still interested in input on the IAT crossmatch with a currently negative screen question.

In the UK, we recommend performing a crossmatch if an atypical alloantibody has ever been detected in a patient's plasma (or, in the case of something like anti-Vel - serum), knowing full well that, on occasions, we will not detect "incompatibility", as, of course, we do not know the "zygotic expression" of most antigens on the red cells of the donor blood, unless we have selected the units specifically.

That having been said, the "rules" in the USA are often very different to the "rules" in the UK!

Lewis antibodies do not cause HDFN and do not need titration.  We do not Lewis phenotype transfusions to patients with anti-Lewis antibodies, but do a manual antiglobulin crossmatch to find units that do not react. I'm sure there are rare patients whose antibodies can cause removal of Lewis positive red cells at an accelerated rate, but this is not something that needs to be considered unless the patient shows signs of hemolysis or rapid red cell removal.  Never come across this in 50 years of practice :).  But never say never in medicine.

6 hours ago, Neil Blumberg said:

Lewis antibodies do not cause HDFN and do not need titration.  We do not Lewis phenotype transfusions to patients with anti-Lewis antibodies, but do a manual antiglobulin crossmatch to find units that do not react. I'm sure there are rare patients whose antibodies can cause removal of Lewis positive red cells at an accelerated rate, but this is not something that needs to be considered unless the patient shows signs of hemolysis or rapid red cell removal.  Never come across this in 50 years of practice :).  But never say never in medicine.

So, you would continue to do IAT XMs for the rest of their life even if the patient's Lewis antibody is not detectable?  

"So, you would continue to do IAT XMs for the rest of their life even if the patient's Lewis antibody is not detectable?"

No, only if the antibody were detectable in the 37 degree/IAT antibody screen.