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Apples and Oranges: Four Definitions of Multiple Chronic Conditions and their Relationship to 30-Day Hospital Readmission

OBJECTIVES: To determine the extent of agreement between four commonly used definitions of multiple chronic conditions (MCCs) and compare each definition’s ability to predict 30-day hospital readmissions.

DESIGN: Retrospective cohort study.

SETTING: National Medicare claims data.

PARTICIPANTS: Random sample of Medicare beneficiaries discharged from the hospital from 2005 to 2009 (n = 710,609).

MEASUREMENTS: Baseline chronic conditions were determined for each participant using four definitions of MCC. The primary outcome was all-cause 30-day hospital readmission. Agreement between MCC definitions was measured, and sensitivities and specificities for each definition’s ability to identify patients experiencing a future readmission were calculated. Logistic regression was used to assess the ability of each MCC definition to predict 30- day hospital readmission.

RESULTS: The sample prevalence of hospitalized Medicare beneficiaries with two or more chronic conditions ranged from 18.6% (Johns Hopkins Adjusted Clinical Groups (ACG) Case-Mix System software) to 92.9% (Medicare Chronic Condition Warehouse (CCW)). There was slight to moderate agreement (kappa = 0.03–0.44) between pair-wise combinations of MCC definitions. CCW-defined MCC was the most sensitive (sensitivity 95.4%, specificity 7.4%), and ACG-defined MCC was the most specific (sensitivity 32.7%, specificity 83.2%) predictor of being readmitted. In the fully adjusted model, the risk of readmission was higher for those with chronic condition Special Needs Plan (c-SNP)-defined MCCs (odds ratio (OR) = 1.50, 95% confidence interval (CI) = 1.47–1.52), Charlson Comorbidity Index–defined MCCs (OR = 1.45, 95% CI = 1.42–1.47), ACG-defined MCCs (OR = 1.22, 95% CI = 1.19–1.25), and CCW-defined MCCs (OR = 1.15, 95% CI = 1.11–1.19) than for those without MCCs.

CONCLUSION: MCC definitions demonstrate poor agreement and should not be used interchangeably. The two definitions with the greatest agreement (CCI, c-SNP) were also the best predictors of 30-day hospital readmissions. J Am Geriatr Soc 65:712–720, 2017.