Hi Sasha, I am not sure exactly how cellquest implements the subtratction feature you described, but performing a channel by channel subtraction is probably the worst way of calculating your percent positive. (Well, putting random numbers on a dart board and throwing a dart to get the value may be worse ;-) Roy overton published a method a while ago that is pretty reasonable, and Mario Roederer and Adam Treistar published a method recently in cytometry that discusses this issue. FCS Express (www.denovosoftware.com) can calculate your percent positive based on the overton subtraction method, and place the resulting positive histogram on a plot for you to use and get statistics on as you would for anything else. -Dave At 03:47 AM 12/11/01 -0800, Sasha Sreckovic wrote: >Hi Craig, > >I believe there is a way to do this in CellQuest. >First you need to overlay histograms in question -> Plots/Overlay menu. >Then go -> Plots/Histogram Tools and highlight both files then click on "Subtract", >which is in >the form of the button, at the bottom middle position of six buttons in this window >(not very >obvious, I agree). Now, you're automatically going to get save dialog box to save >new subtracted >file with default name e.g. Data.001-Data.002. This is a new FCS file that you can >analyse >separately. > >Cheers, Sasha. >
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