A modified Elixhauser score for predicting in-hospital mortality in internal medicine admissions

In-hospital mortality (IHM) is an indicator of the quality of care provided. The two most widely used scores for predicting IHM by International Classification of Diseases (ICD) codes are the Elixhauser (EI) and the Charlson Comorbidity indexes. Our aim was to obtain new measures based on internal medicine ICD codes for the original EI, to detect risk for IHM.

This single-center retrospective study included hospital admissions for any cause in the department of internal medicine between January 1, 2000, and December 31, 2013, recorded in the hospital database. The EI was calculated for evaluation of comorbidity, then we added age, gender and diagnosis of ischemic heart disease. IHM was our outcome. Only predictors positively associated with IHM were taken into consideration and the Sullivan's method was applied in order to modify the parameter estimates of the regression model into an index.

We analyzed 75,586 admissions (53.4% females) and mean age was 72.7±16.3years. IHM was 7.9% and mean score was 12.1±7.6. The points assigned to each condition ranged from 0 to 16, and the possible range of the score varied between 0 and 89. In our population the score ranged from 0 to 54, and it was higher in the deceased group. Receiver operating characteristic curve of the new score was 0.721 (95% CI 0.714-0.727, p<0.001).

In order to make prognostic assessment, the use of a score could be of help in targeting interventions in older adults, identifying subjects at high risk for IHM.