Discriminative Ability of Elixhauser's Comorbidity Measure is Superior to Other Comorbidity Scores for Inpatient Adverse Outcomes After Total Hip Arthroplasty

Identifying patients at highest risk for a complex perioperative course following total hip arthroplasty (THA) is more important than ever in order to educate patients, optimize outcomes, and to minimize cost and length of stay. There are no known studies comparing the clinically relevant discriminative ability of 3 commonly used comorbidity indices for adverse outcomes following THA: Elixhauser Comorbidity Measure (ECM), the Charlson Comorbidity Index (CCI), and the modified Frailty Index (mFI). Patients undergoing THA were extracted from the 2013 National Inpatient Sample. The discriminative ability of ECM, CCI, and mFI, as well as the demographic factors age, body mass index, and gender for the occurrence of index admission Centers for Medicare & Medicaid Services procedure-specific complication measures, extended length of hospital stay, and discharge to a facility were assessed using the area under the curve analysis from receiver operating characteristic curves. ECM outperformed CCI and mFI for the occurrence of all 5 adverse outcomes. Age outperformed gender and obesity for the occurrence of all 5 adverse outcomes. ECM (the best performing comorbidity index) outperformed age (the best performing demographic factor) in discriminative ability for the occurrence of 3 of 5 adverse outcomes. The less commonly used ECM outperformed the more often utilized CCI and newer mFI as well as demographic factors in correctly preoperatively identifying patients' probabilities of experiencing an adverse outcome suggesting that wider adoption of ECM should be considered in both identifying likelihoods of adverse patient outcomes and for research purposes in future studies.