Coefficient of variation:

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In standard condition when same particle passing through the laser beam produce same light scattered and florescence pulse but during experiment always some variation in instrument which cause some variation in pulse even though particle is same, due to sample flow, laser intensity, laser alignment, beam focusing and detection. these variation leads to variation in histogram and importnat is to determine that variation is due to the instrument or particle variation or both. this variation can be calculated by coefficient of variation (cv) no a good uniform test sample such as flurescent beads.

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CV=(SD/Mean) x 100

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SD= standard deviation (average value for the parameters)

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normal CV was calculated and any increse in CV indicate that the instrument setting may be changing and result in broadening of histogram. however if CV are good and still histogram are broadening then phenomenon is genunie.

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Quality Control tests – we check alignment of our cytometers using single peak beads which are very uniform and will have low intrinsic variation and therefore a low CV – we can monitor this and it tells us that our cytometer is performing optimally.