Flow rates and the effect on data

From: Rosson, Dan (RossonD@MLHS.ORG)
Date: Thu Jun 14 2001 - 06:54:30 EST


I have what for some of you will be an elementary question. I've asked 3
people who've been in the business 20 times longer than I have and are in a
position to know, and I've gotten 2 different answers.

 A FACScan has a limit as to how many cells it can count per second. If the
cells are going through the flow cell faster than the reset time allows it
to count, what happens to your data?
Does the FACscan simply "ignore" a percentage of the cells, in which case
one doesn't really care because if the sample is that concentrated you have
more than enough cells to do your analysis? Or, does the instrument see
partial signals as the next cell arrives in the flow cell before the
instrument has had time to reset itself, thus giving rise to lower MFI's and
wider CV's, in which case one does care?

A search of the e-mail archives uncovered related discussions that imply to
me that the former explanation (it ignores some cells) is the answer, but
I'd like some reassurance.





Dan Rosson Ph.D.
Lankenau Medical Research Center



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