title: Charlson and Rx-Risk comorbidity indices were predictive of mortality in the Australian health care setting.
abstract: OBJECTIVE
  To compare the performance of Charlson index and Rx-Risk score using data from Australian Department of Veterans' Affairs.
  
  
  METHODS
  A study of older adults (N=94,714) who had both Charlson and Rx-Risk scores based on their hospital diagnoses and prescription medication dispensings during the baseline year (January 2005-December 2005). Predictive ability of 1-year and 3-year mortality was compared by Akaike information criterion model fit statistic and c statistic in logistic regression models. We also compared the scores for identifying specific medical conditions.
  
  
  RESULTS
  Both indices were significant predictors of all-cause mortality (P<0.0001). Of the population identified with a condition from either score, Rx-Risk score identified more than 95% of patients with gastric, respiratory, or cardiovascular condition, compared with Charlson index only identifying 2%, 31%, and 14%, respectively. The indices were comparable regarding diabetes. The Charlson index identified 83% of patients with dementia and 67% of those with cancers, whereas Rx-Risk score identified 38% and 43%, respectively.
  
  
  CONCLUSIONS
  Both the Charlson and Rx-Risk scores predict mortality, but neither index identified all comorbidities. Based on data availability, preferences, and research purposes, investigators can use either Charlson index or Rx-Risk score to adjust for comorbidity.
authors.affiliation: Quality Use of Medicines and Pharmacy Research Centre, Sansom Institute for Health Research, University of South Australia, Adelaide, SA 5001, Australia. christine.lu@unisa.edu.au
authors.forename: Christine Y
authors.initials: CY
authors.lastname: Lu
authors.forename: John
authors.initials: J
authors.lastname: Barratt
authors.forename: Agnes
authors.initials: A
authors.lastname: Vitry
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Roughead
mesh_terms: D000368:Aged; D001315:Australia / Q000453:epidemiology; D015897:Comorbidity; D005260:Female; D005544:Forecasting; D006305:Health Status Indicators; D006801:Humans; D016015:Logistic Models; D008297:Male; D009026:Mortality; D011795:Surveys and Questionnaires / Q000592:standards; D014728:Veterans / Q000706:statistics & numerical data*