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

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Abstract

Background

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).

Methods

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.

Results

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.

Conclusion

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.

Section snippets

Patient Sample

Patients for this study were drawn from the 2013 National Inpatient Sample (NIS). The dataset is an approximated sample of 20% of all hospital discharges from the United States. Patients are included regardless if they are insured through Medicare/Medicaid, private insurance, or no insurance at all [25].

The large patient population in NIS allows for sufficient statistical power to draw clinically meaningful conclusions based on a nationally representative population. NIS has the additional

Results

In total, 68,680 patients were identified for the study. Average age was 65.1 ± 11.8 years old (mean ± standard deviation). Over half of the patients were female (55.8%), and 17.1% of patients were obese (Table 3). The summary statistics regarding the studied comorbidity indices demonstrated a median (interquartile range) of 0 (0-1) for the CCI, 2 (1-3) for the ECM, and 0.09 (0-0.09) for the mFI (Table 3).

Approximately 1% of patients experienced some type of CMS-PSCM postoperative general

Discussion

Despite advances in surgical and anesthesia technique, THA is inherently associated with perioperative adverse events [33], [34], [35]. As the demand for THA rises and the elderly population increases, more patients who are older with greater comorbidities will undergo THA procedures [1], [33], [36]. However, despite an increasing number of sicker patients undergoing THA, there is great push toward shorter hospital length of stay following THA in order to reduce healthcare cost [37]. It is

Conclusions

In conclusion, the findings of this study indicate that ECM outperforms CCI and mFI for correctly identifying the probability of the occurrence of several specific and standardized general health adverse outcomes as well as adverse hospital metrics, and that this is mildly improved by considering patient age. The collection of the information necessary to calculate the ECM may help in optimizing clinical pathways and improve controlling for the effect of comorbid diseases in future THA research.

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    One or more of the authors of this paper have disclosed potential or pertinent conflicts of interest, which may include receipt of payment, either direct or indirect, institutional support, or association with an entity in the biomedical field which may be perceived to have potential conflict of interest with this work. For full disclosure statements refer to https://doi.org/10.1016/j.arth.2017.08.032.

    Ethical Review Committee Statement: This study has been given an exemption from the senior author's Institutional Review Board under federal regulation 45 CFR 46.101(b) (4).

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