data representation

Rafael Nunez rafaeln at
Sat Aug 8 07:29:24 EST 1998

Dear Jackie, my experience is that you can present mean fluorescent
intensity (MFI) of the whole population if you have a single cell
population in a single peak, but MFI of the whole population when you have
a dual peak could not reflect properly all your data. In that situation,
the % of the population that you have already selected with your M1 would
give you a quite fair representation of your data.
A few months ago, we had in this list an interesting discussion about the
use of isotype matched antibodies for setting up the negative controls and
M1(s), that will give you the peace of mind with your M1 without dependent
on of the  "Flow Gods"  ( I still remember Mario's statesment that almost
kill my teachers at Iowa and sent me to request my tuition reimbursement).
With that controls you can compare the results within each experiment, but
it is not good practice to compare with another experiments. However, the
best that you can do is to show your plots (an imagen is better than
thousand words, ask CNN) within one experiment, put MFI or % and hope that
the  "Flow Gods" protect you of reviewers that are more worried because of
the word "FACS" than the content and meaning of your work (my five cents).
Cheers Rafael
>Dear Flow-ers:
>Various users at my company are having very heated discussions on what
>number to use
>to beat reprent fluorescent intensity. Some users are using mean of M1(%
>positive cells)
>to describe fluorescent intensity. I believe this not is inaccurate because
>your using
>the mean of 20-30% of the cell population and I believe the mean of the
>entire population
>(not just M1) to be a much more accurate determination of fluorescence
>I myself prefer to use percent positive cells as opposed to mean
>fluorescent intensity
>to describe my data. I also explained to people that you cannot compare
>mean fluorescent
>intensities from this weeks experiment versus last weeks experiment because
>the means
>will vary considerably depending on were the negative control is set, if
>the planets are
>in line with Jupiter, and the "Flow Gods" see fit to smile on you. Any
>feedback on how
>people represent their data is greatly appreciated. Thanks in advance to
>Ariad Pharmaceuticals

                                    (o o)
    ___/\_    | Rafael Nunez                  mailto:rafaeln at
   /    o \/| | University Inst.for Virology
  /        _| | Winterthurerstr. 266a         Telephone: (+41) 1 6358710
 /_/\__/-\/   | 8057 Zurich SWITZERLAND       Faximile : (+41) 1 6358911

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