A method in which a multiplicative ratio approach is used to remove the effects of the unwanted background fluorescence when making fluoroescence polarization (FP) measurements rather than the conventional subtractive approach, thus preserving both the precision and accuracy of the FP measurements, is disclosed. The method comprises selecting an appropriate multiplicative ratio, then calculating the selected multiplicative ratio using sample measurements. The calculated multiplicative ratio is multiplied by an appropriate value in a standard FP measurement equation or an appropriate value in an equation derived from a standard FP measurement equation. After this, the corrected FP measurement is calculated. When such multiplicative ratios are applied to the appropriate value or values in an FP measurement equation, the effects of background noise can be reduced without decreasing the precision of the FP measurements.
Ratiometric background correction for fluorescence polarization assays