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A comparison of two comorbidity instruments in arthritis
S E Gabriel1, C S Crowson, W M O'Fallon
1Department of Health Sciences Research, Mayo Foundation, Rochester, Minnesota 55905, USA. gabriel.sherine@mayo.edu
Journal of Clinical Epidemiology
|December 2, 1999
Summary
Comorbidity measurement instruments like Charlson CM index and Index of Coexistent Diseases both predict mortality in arthritis patients. The Index of Coexistent Diseases provides independent mortality prediction, even when accounting for the Charlson CM index.
Area of Science:
- Epidemiology
- Health Outcomes Research
- Rheumatology
Background:
- Comorbidity (CM) significantly impacts health outcomes, costs, and epidemiological study confounding.
- Selecting appropriate CM measurement instruments is challenging due to limited comparative data across disease settings.
Purpose of the Study:
- To compare the performance of two CM instruments, Charlson CM index (Charl) and Index of Coexistent Diseases (ICED), in predicting mortality.
- To assess if ICED offers independent predictive value for mortality beyond Charl.
Main Methods:
- Collected CM data from medical records for rheumatoid arthritis (RA), osteoarthritis (OA), and no arthritis (NA) cohorts.
- Utilized Charlson CM index (Charl) and Index of Coexistent Diseases (ICED) for CM assessment.
- Employed Cox proportional hazards modeling to analyze the impact of Charl and ICED on survival, adjusting for age, sex, and disease status.
Main Results:
- Comorbidity levels were highest in RA, intermediate in OA, and lowest in NA by both instruments.
- Both Charl and ICED were significant predictors of mortality (P<0.0001) after adjustments.
- ICED remained a highly significant predictor of mortality even after adjusting for Charl.
Conclusions:
- Estimating comorbidity using ICED, which includes impairment and disability, is feasible from medical records.
- ICED provides independent mortality prediction, offering additional value beyond traditional measures like Charl.