The choice of measure is likely to be based on the suitability of the measure for the data available as well as the outcome of interest. The Charlson index, ACG System,diseases counts,and prescription counts can all be calculated from patient records,and these measures are particularly suitable for cross-sectional studies based on electronic records or administrative data. Both the CIRS and DUSOI, however,require judgment about individual patient and cannot be automate for use with large volumes of data.
Measures based on routine data may be easy to use,but ease of use needs to be balanced against the quality of the data. All measures are dependent on the range of conditions recorded,how accurately and recently these conditions were recorded,and whether there is information about the severity and impact of conditions. Measures using clinician ratings or patient self-report will be up-to-date and may be more accurate at predicting functional outcome if they include