title: Common comorbidity scales were similar in their ability to predict health care costs and mortality.
abstract: OBJECTIVE
  To compare the ability of commonly used measures of medical comorbidity (ambulatory care groups [ACGs], Charlson comorbidity index, chronic disease score, number of prescribed medications, and number of chronic diseases) to predict mortality and health care costs over 1 year.
  
  
  METHODS
  A prospective cohort study of community-dwelling older adults (n=3,496) attending a large primary care practice.
  
  
  RESULTS
  For predicting health care charges, the number of medications had the highest predictive validity (R(2)=13.6%) after adjusting for demographics. ACGs (R(2)=16.4%) and the number of medications (15.0%) had the highest predictive validity for predicting ambulatory visits. ACGs and the Charlson comorbidity index (area under the receiver operator characteristic [ROC] curve=0.695-0.767) performed better than medication-based measures (area under the ROC curve=0.662-0.679) for predicting mortality. There is relatively little difference, however, in the predictive validity across these scales.
  
  
  CONCLUSIONS
  In an outpatient setting, a simple count of medications may be the most efficient comorbidity measure for predicting utilization and health-care charges over the ensuing year. In contrast, diagnosis-based measures have greater predictive validity for 1-year mortality. Current comorbidity measures, however, have only poor to moderate predictive validity for costs or mortality over 1 year.
authors.affiliation: Indiana University Center for Aging Research, 1050 Wishard Boulevard, RG6, Indianapolis, IN 46202, USA. tperkins@regenstrief.org
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Perkins
authors.forename: Kurt
authors.initials: K
authors.lastname: Kroenke
authors.forename: Jürgen
authors.initials: J
authors.lastname: Unützer
authors.forename: Wayne
authors.initials: W
authors.lastname: Katon
authors.forename: John W
authors.initials: JW
authors.lastname: Williams
authors.forename: Carol
authors.initials: C
authors.lastname: Hope
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Callahan
mesh_terms: D001741:Black or African American; D000368:Aged; D000553:Ambulatory Care / Q000191:economics; D002423:Cause of Death; D002908:Chronic Disease; D015897:Comorbidity; D005260:Female; D017048:Health Care Costs; D006305:Health Status Indicators; D006801:Humans; D008297:Male; D015233:Models, Statistical; D019338:Polypharmacy; D011237:Predictive Value of Tests; D011379:Prognosis; D011446:Prospective Studies