Use this calculation for cell-culture or microscopy observations collected with one counting rule, assay gate, calibration, and unit convention. It is suited to documenting dilution, growth, labeling, geometry, or population fractions.

BrdU-labeled nuclei

An integer count greater than or equal to 0.

Total nuclei

An integer count greater than or equal to 0.

The implementation follows this calculation rule: Compute the BrdU labeling index as the percentage of BrdU-labeled nuclei.^[1]

Labeling index

The calculated labeling index in %.

Counts and fluorescence measurements can be biased by clumping, debris, segmentation, gating, background signal, saturation, sampling fields, or unequal viability. A calculated percentage does not identify the biological mechanism behind a change. Ratios and percentages become unstable when their denominator is small, uncertain, or defined differently between samples.

Retain representative images or cytometry plots and include biological replicates. Orthogonal viability, proliferation, apoptosis, or direct counting assays can distinguish effects that a single cell metric conflates.

• BrdU Incorporation Rate

  Compute the percentage of BrdU positive cells relative to the total counted cell population.

• Necrotic Index

  Compute the percentage of necrotic cells in a counted cell population.

• Apoptosis %

  Calculate the apoptosis percentage from apoptotic and total cell counts.