Nicolette:

You could try the AABB for additional information, but I think many blood
banks QC their screen cells with Anti-D, although some dilute it before use.
You could purchase a commercial QC kit, some of which use Anti-Fya (I think)
as the sole source of a positive reaction.  The FDA may be questioning your
use of a strong reagent against a strong antigen as a QC procedure, or
possibly citing a deficiency in your QA plan.

The purpose of the daily QC exercise is to verify that the screen cells can
still pick up weak antibodies in patient sera; a visual check of the cells
and supernatant won't detect much degradation until its way too late.  Most
sites leave their reagents cells sitting at Room Temp, and while probably OK
for the reverse cells -- the ABO antigens are fairly hardy -- some of the
antigens on screen cells are more susceptible to that kind of "abuse."

Years ago, I remember reading that Anti-c degrades more rapidly than other
common anitgens at RT, and since it's rather inexpensive and since screen
cells typically include R1R1 and R2R2 cells, we used to sequestere a lot and
weekly diluted an aliquot to a 1+ reaction (stored at 4 C).  We also QC'd
our panels with the same reagent, and documented our decision to use it and
the validation as part of our Quality Plan.  I'm not sure if this procedure
would be acceptable to the FDA, though, since they may ask you for a
thorough validation -- it would be cheaper to buy a commerical QC kit !!

Good Luck !!

Larry C. Smrz, MT(ASCP)SBB
AABB Assessor
Indianapolis, IN