Stain index

The Stain Index is a measure of reagent performance on a specific cytometer, a normalized signal over background metric.

Stain Index = Brightness / Width of negative = (MFI positive – MFI negative) / 2rSD negative

∆ The brightness is a function of the assay (antigen density, fluorochrome used).

∆ The width of the negative is a function of: Instrument performance (Qr, Br, and SDen) and the assay (Fluorescence spillover / compensation), The cell population.

Corelation of Stain Index, Qr, and Br

If stain index is high then Qr is high while Br is low but at low SI it was inveresed.

Courtesy : BD Biosiences