30-day mortality in patients after hip fracture surgery: A comparison of the Charlson Comorbidity Index score and ASA score used in two prediction models.

Abstract

To compare the Charlson Comorbidity Index (CCI) and American Society of Anesthesiologists (ASA) Physical Status Classification used in two prediction models for 30-day mortality after hip fracture surgery. Data from 3651 patients (mean age: 83 years) from a Norwegian University Hospital were retrospectively obtained and randomly divided into two cohorts: a model cohort (n = 1825) to develop two prediction models with CCI and ASA as the main predictors, and a validation cohort (n = 1826) to assess the predictive ability of both models. A receiver operating characteristic (ROC) curve determined the best model to predict mortality. Area under the ROC curve at 30 days was 0.726 (p = 0.988) for both the CCI- and ASA-model. The chosen cut-off-points on the ROC curve for CCI- and ASA-model corresponded to similar model sensitivities of 0.657 and specificities of 0.680 and 0.679, respectively. Hence, each model predicts correctly 66% (n = 96) of the mortalities and 68% (n = 1132 and n = 1131) of the survivals. 23% (n = 33) of the mortalities were predicted by neither model. The CCI- and ASA-model had equal predictive ability of 30-day mortality after hip fracture. Considering the effort involved in calculating Charlson Comorbidity Index score, the ASA score may be the preferred tool to predict the 30-day mortality after hip fracture.