In Search of the Perfect Comorbidity Measure for Use with Administrative Claims Data: Does It Exist?

Department of Family Medicine, University of Washington, Seattle, Washington 98195-4982, USA.
Medical Care (Impact Factor: 3.23). 09/2006; 44(8):745-53. DOI: 10.1097/01.mlr.0000223475.70440.07
Source: PubMed


Numerous measures of comorbidity have been developed for health services research with administrative claims.
We sought to compare the performance of 4 claims-based comorbidity measures.
We undertook a retrospective cohort study of 5777 Medicare beneficiaries ages 66 and older with stage III colon cancer reported to the Surveillance, Epidemiology, and End Results Program between January 1, 1992 and December 31, 1996.
Comorbidity measures included Elixhauser's set of 30 condition indicators, Klabunde's outpatient and inpatient indices weighted for colorectal cancer patients, Diagnostic Cost Groups, and the Adjusted Clinical Group (ACG) System. Outcomes included receipt of adjuvant chemotherapy and 2 year noncancer mortality.
For all measures, greater comorbidity significantly predicted lower receipt of chemotherapy and higher noncancer death. Nested logistic regression modeling suggests that using more claims sources to measure comorbidity generally improves the prediction of chemotherapy receipt and noncancer death, but depends on the measure type and outcome studied. All 4 comorbidity measures significantly improved the fit of baseline regression models for both chemotherapy receipt (baseline c-statistic 0.776; ranging from 0.779 after adding ACGs and Klabunde to 0.789 after Elixhauser) and noncancer death (baseline c-statistic 0.687; ranging from 0.717 after adding ACGs to 0.744 after Elixhauser).
Although some comorbidity measures demonstrate minor advantages over others, each is fairly robust in predicting both chemotherapy receipt and noncancer death. Investigators should choose among these measures based on their availability, comfort with the methodology, and outcomes of interest.

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    • "Patient co-morbidity was estimated using the adjusted clinical group (ACG) method [14]. Each patient was assigned to any number of 12 collapsed aggregate diagnosis groups (CADGs), defined by constellations of conditions of similar severity and chronicity based on ICD versions 9 and 10 (ICD-9 and ICD-10) and on OHIP coding using a 2-year review period [15]. We identified whether patients were admitted to hospital at the time of a closed reduction by the presence of a DAD or an SDS entry associated chronologically with the service date of the index event OHIP elbow relocation fee code. "
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    • "The number of ADGs was calculated from administrative data for each year the child was between the ages 12 and 17; this excludes routine visits (for immunizations, for example) before the age of 12 [25]. This index is one of several claims-based measures similarly correlated with mortality [54]. The mean morbidity score of all cohort members was 9.69. "
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