In this report by Dartmouth Institute, rates of utilisation (per patient) were reported by year and regions. The input measure of utilisation were said to have been adjusted for differences in age, sex, race, primary chronic condition using ordinary linear regression and poisson regression (see page 3 and 38). I think it also means it is conditioned on these variables.
I am wondering how was it done. Was regression model fitted with a particular utilisation variable (e.g. hospital days) as dependent variable and the variables they want to adjust for as independent variable? Subsequently was predicted values used to get the rates?
[Edit]I have an additional questions. Is this method valid? Appreciate if someone could show how conditional expectation is derived from log-linked generalized linear model and how to perform it in R. A working example would be the best.