The need to change the model is consistent with improvements in care. This is the second time we have changed the predictive algorithms. Originally data was obtained from 32 institutions. We eliminated 16 of the original 32 institutions since the data was more than 5 years old. The predictors were developed by fitting a multiple logistic regression model to the observed mortality data.
R is given by the logistic regression models.
The logistic model-fit over the 14 ordered risk intervals is excellent in both split samples separately, as well as, over six ordered age and six diagnostic categories of the patients.