The University of Iowa Carver College of Medicine

Flow Cytometry Facility

Flow Cytometry Fundamentals


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  • Calculation for Comparing Populations
  • Staining Index
    This calculation can be used for normalizing the relationship between positive and negative populations to compare treated and untreated samples.

    SI = (MFIpos - MFIneg ) / (2 X SDneg)

    SI = staining index
    MFI = median, geometric-mean, or mean fluorescence intensity
    SD = standard deviation.

    Note: Population average fluorescence intensity values can be skewed depending on the population distribution. Median fluorescence intensity is less skewed than geometric-mean fluorescence intensity and geometric-mean fluorescence intensity is less skewed than mean fluorescence intensity for log-normal populations (populations that look gaussian when plotted on a log scale).

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