Comparison of a polypharmacy-based scale with Charlson comorbidity index to predict 6-month mortality in chronic complex patients after an ED visit

Abstract

Aims: The aim of this study was to test whether a newly designed polypharmacy-based scale would perform better than Charlson's Comorbidity Index (CCI) to predict outcomes in chronic complex adult patients after a reference Emergency Department (ED) visit. Methods: We built a polypharmacy-based scale with prespecified drug families. The primary outcome was 6-month mortality after the reference ED visit. Predefined secondary outcomes were need for hospital admission, 30-day readmission, and 30-day and 90-day mortality. We evaluated the ability of the CCI and the polypharmacy-based scale to independently predict 6-month mortality using logistic regression, receiver operating characteristic (ROC) curves, and cumulative survival curves using Kaplan-Meier estimates and the log-rank test for three-category distributions of the polypharmacy-based scale and the CCI. Finally, we sought to replicate our results in two different external validation cohorts. Results: We included 201 patients (53.7% women, mean age = 81.4 years), 162 of whom were admitted to the hospital at the reference ED visit. In separate multivariable analyses accounting for gender, age and main diagnosis at discharge, both the polypharmacy-based scale (P < .001) and the CCI (P = .005) independently predicted 6-month mortality. The polypharmacy-based scale performed better in the ROC analyses (area under the curve [AUC] = 0.838, 95% confidence interval [CI] = 0.780-0.896) than the CCI (AUC = 0.628, 95% CI = 0.548-0.707). In the 6-month cumulative survival analysis, the polypharmacy-based scale showed statistical significance (P < .001), whereas the CCI did not (P = .484). We replicated our results in the validation cohorts. Conclusions: Our polypharmacy-based scale performed significantly better than the CCI to predict 6-month mortality in chronic complex patients after a reference ED visit.