Evaluating comorbidity scores based on health service expenditures.

Objective: To describe the performance of Charlson Comorbidity Index (CCI) specifications among Medicare beneficiaries and subgroups.

Data sources: Medicare data for beneficiaries covered by Parts A and B and not Medicare Advantage throughout 2007.

Study design: We evaluated several CCI specifications, particularly a model using expenditures related to Charlson categories, to predict 1 year mortality.

Data collection/extraction methods: Data were obtained from the Chronic Condition Data Warehouse.

Principal findings: The use of Charlson related expenditures did not result in improved mortality prediction. CCI models perform less well in population subgroups with higher underlying mortality risks based on age and chronic conditions.

Conclusions: Relatively simple models provide quite adequate discrimination compared to more sophisticated models. Our proposed and more sophisticated model, which added in expenditure information, did not perform as well as much more easily executed methods.