Development of a comorbidity index using physician claims data

Important comorbidities recorded on outpatient claims in administrative dat asets may be missed in analyses when only inpatient care is considered. Usi ng the comorbid conditions identified by Charlson and colleagues, we develo ped a comorbidity index that incorporates the diagnostic and procedure data contained in Medicare physician (Part B) claims. In the national cohorts o f elderly prostate (n = 28,868) and breast cancer (n = 14,943) patients ass essed in this study, less than 10% of patients had comorbid conditions iden tified when only Medicare hospital (Part A) claims were examined. By incorp orating physician claims, the proportion of patients with comorbid conditio ns increased to 25%. The new physician claims comorbidity index significant ly contributes to models of 2-year noncancer mortality and treatment receiv ed in both patient cohorts. We demonstrate the utility of a disease-specifi c index using an alternative method of construction employing study-specifi c weights. The physician claims index can be used in conjunction with a com orbidity index derived from inpatient hospital claims, or employed as a sta nd-alone measure. (C) 2000 Elsevier Science Inc. All rights reserved.