What is critical to exclude dead cells in flow cytometry analysis?

In flow cytometry analysis, excluding dead cells is essential for obtaining accurate results. The inclusion of a cell viability dye is critical because it specifically distinguishes between live and dead cells. When a viability dye is added to the cell sample, it permeates only dead cells, allowing for fluorescence to be measured only in those cells that are not intact and therefore non-viable. This process ensures that the data collected reflects the characteristics of live, functioning cells, which is particularly important when analyzing cell populations for purposes such as immunophenotyping or assessing cell health.

Other options, while they may impact the flow cytometry results, do not directly relate to the exclusion of dead cells. Proper excitation of fluorophores is necessary for effective signaling and detection of the fluorescent markers associated with the live population, but it doesn't inherently distinguish between live and dead cells. Maximizing laser intensity can enhance the detection sensitivity but does not provide information on cell viability. Minimizing fluidics flow rate may affect the resolution of detection and the stability of cells passing through the laser but is not a method for identifying dead cells. Therefore, the inclusion of a cell viability dye remains the key factor in accurately excluding dead cells from analysis.