The ability of comorbidity indices to predict mortality in an orthopedic setting: a systematic review

Several comorbidity indices have been created to estimate and adjust for the burden of comorbidity. The objective of this systematic review was to evaluate and compare the ability of different comorbidity indices to predict mortality in an orthopedic setting.

A systematic search was conducted in Embase, MEDLINE, and Cochrane Library. The search were constructed around two primary focal points: a comorbidity index and orthopedics. The last search were performed on 13 June 2019. Eligibility criteria were participants with orthopedic conditions or who underwent an orthopedic procedure, a comparison between comorbidity indices that used administrative data, and reported mortality as outcome. Two independent reviewers screened the studies using Covidence. The area under the curve (AUC) was chosen as the primary effect estimate.

Of the 5338 studies identified, 16 met the eligibility criteria. The predictive ability of the different comorbidity indices ranged from poor (AUC < 0.70) to excellent (AUC ≥ 0.90). The majority of the included studies compared the Elixhauser Comorbidity Index (ECI) and the Charlson Comorbidity Index (CCI). In-hospital mortality was reported in eight studies reporting AUC values ranging from 0.70 to 0.92 for ECI and 0.68 to 0.89 for CCI. AUC values were generally lower for all other time points ranging from 0.67 to 0.78. For 1-year mortality the overall effect size ranging from 0.67 to 0.77 for ECI and 0.69 to 0.77 for CCI.

The results of this review indicate that the ECI and CCI can equally be used to adjust for comorbidities when analyzing mortality in an orthopedic setting.

The protocol for this systematic review was registered on PROSPERO, the International Prospective Register of Systematic Reviews on 13 June 2019 and can be accessed through record ID 133,871.