Differences in the Predictive value of Elixhauser Comorbidity Index and the Charlson Comorbidity indices in patients with hand infections

Purpose: Hand infections are a common source of potentially debilitating morbidity, particularly in patients with comorbid disease. We hypothesize that there is a difference in predictive value between two commonly used comorbidity indices for the prognosis of hand infections, which may have clinical implications in the management of these conditions. Methods: The Nationwide Inpatient Sample 2001–2013 database was queried for hand infections using International Classification of Diseases, Ninth Revision codes. The Elixhauser (ECI) and Charlson (CCI) comorbidity scores were calculated based on validated sets of ICD-9 codes. Primary outcomes included mortality, prolonged length of stay (LOS, defined as >95 percentile), discharge destination, and postoperative complications. Indices were compared using receiver operating characteristic (ROC) curves and the areas under the curve (AUC). If confidence intervals overlapped, significance was determined using the DeLong method for correlated ROC curves. This is a validated, non-parametric comparison used for the calculation of the difference between two AUCs. Results: A weighted total of 1,511,057 patients were included in this study. The majority were Caucasian (57.1%) males (61.4%). Complication rates included 0.9% mortality, 5.3% prolonged length of stay, 25.3% discharges to non-home destinations, and 5.3% post-operative complications. The ECI and CCI each demonstrated good predictive value for mortality, but poor predictive value for non-routine discharge, prolonged LOS, and post-operative complications. There was a significantly increased likelihood of each complication with increasing comorbidity score for both indices, with the greatest odds ratio in the ECI ≥4 cohort. Conclusions: The CCI was superior in predicting mortality while the ECI was superior in predicting non-routine discharge, prolonged length of stay, and postoperative complications, but these indices may not be clinically relevant. While both represent good predictive models, a score specifically designed for patients with hand infections may have superior prognostic value. Level of evidence: Level IV.