title: Searching for an improved clinical comorbidity index for use with ICD-9-CM administrative data.
abstract: We studied approaches to comorbidity risk adjustment by comparing two ICD-9-CM adaptations (Deyo, Dartmouth-Manitoba) of the Charlson comorbidity index applied to Massachusetts coronary artery bypass surgery data. We also developed a new comorbidity index by assigning study-specific weights to the original Charlson comorbidity variables. The 2 ICD-9-CM coding adaptations assigned identical Charlson comorbidity scores to 90% of cases, and specific comorbidities were largely found in the same cases (kappa values of 0.72-1.0 for 15 of 16 comorbidities). Meanwhile, the study-specific comorbidity index identified a 10% subset of patients with 15% mortality, whereas the 5% highest-risk patients according to the Charlson index had only 8% mortality (p = 0.01). A model using the new index to predict mortality had better validated performance than a model based on the original Charlson index (c = 0.74 vs. 0.70). Thus, in our population, the ICD-9-CM adaptation used to create the Charlson score mattered little, but using study-specific weights with the Charlson variables substantially improved the power of these data to predict mortality.
authors.affiliation: Health Care Research Unit, Boston University Medical Center, MA 02118, USA.
authors.forename: W A
authors.initials: WA
authors.lastname: Ghali
authors.forename: R E
authors.initials: RE
authors.lastname: Hall
authors.forename: A K
authors.initials: AK
authors.lastname: Rosen
authors.forename: A S
authors.initials: AS
authors.lastname: Ash
authors.forename: M A
authors.initials: MA
authors.lastname: Moskowitz
mesh_terms: D000368:Aged; D015897:Comorbidity; D001026:Coronary Artery Bypass / Q000401:mortality*; D003327:Coronary Disease / Q000453:epidemiology* / Q000401:mortality / Q000601:surgery; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D015999:Multivariate Analysis; D015203:Reproducibility of Results