Question 1 of 6 Fundamentals Concept
Why are fluorescence compensation controls important?
Short answer
Fluorophores emit into more than one detector, so the measured signal in one channel may partly originate from another dye. Single-color reference controls estimate this spillover for conventional compensation or spectral unmixing. Correcting the average spillover does not remove all measurement spread.
Why
Fluorescence signatures overlap. Without calibrated reference controls, a bright CD3 fluorophore may appear to create an unrelated CD19-positive population in another detector. Run instrument-appropriate single-color controls with the same fluorophores, relevant reagent lots and suitable positive and negative reference populations.
For conventional flow, calculate compensation coefficients. For spectral flow, unmix full spectral signatures while accounting for autofluorescence as supported by the instrument workflow. Then examine bivariate plots for overcompensation or undercompensation and test the panel on actual sample types.
Compensation adjusts systematic signal overlap, but spreading error persists because photon and measurement noise vary between events. High-intensity dyes near dim coexpressed targets may therefore obscure the gate even after mathematically correct compensation. Choose fluorochromes with spreading in mind and use FMO controls to support difficult gates.
Never substitute a similar-looking dye for the exact fluorophore in the reference.
Common mistakes
- Assuming compensation eliminates spillover-induced variance or that an unstained sample replaces single-stain controls
The interviewer might ask next
Why could a correctly compensated panel still fail to resolve a dim marker?