Measure that can be used in comparison of adverse reactions to drugs, or other exposures, based solely on the component of risk due to the exposure or drug under investigation, removing the risk due to background exposure experienced by all in the population. The relative excess risk, R, is given by

R = (R1-R0) / (R2-R0)

where R1is the rate in the population, R2 is the rate in the comparison population, and R0is the rate in the general population.

Note: Rate is used here as in epidemiology.