title: Standard Comorbidity Measures Do Not Predict Patient-reported Outcomes 1 Year After Total Hip Arthroplasty.
abstract: BACKGROUND
  Comorbidities influence surgical outcomes and therefore need to be included in risk adjustment when predicting patient-reported outcomes. However, there is no consensus on how best to use the available data about comorbidities in registry-based predictive models.
  
  
  OBJECTIVE
  The purposes of this study were (1) to determine whether the International Classification of Diseases, 10(th) Revision (ICD-10)-based comorbidity measures (Elixhauser, Charlson, and Royal College of Surgeons Charlson) offer added value in explaining patients' health-related quality of life (HRQoL), pain, and satisfaction after total hip arthroplasty (THA) when preoperative HRQoL, pain, and Charnley classification were known; and (2) to determine the ideal timeframe for recording the different diagnoses that serves as the basis for comorbidity measure calculations.
  
  
  METHODS
  There were 22,263 patients who had undergone THA with complete pre- and postoperative patient-reported outcome measures (PROMs) included in the Swedish Hip Arthroplasty Register between 2002 and 2007. The three comorbidity indices were calculated with ICD-10 codes identified in the Swedish National Patient Register from 1, 2, and 5 years before the patient underwent THA. The impact of the comorbidity indices on the PROM scores (EQ-5D index, EQ visual analog scale [VAS], pain VAS, and satisfaction VAS) was modeled with linear regression where the 1-year patient postoperative outcome score was the dependent variable and independent variables included patient preoperative Charnley classification, preoperative HRQoL and pain, and comorbidity indices. The partial R(2) value indicated how much each variable uniquely contributed to the predictive capacity of the model.
  
  
  RESULTS
  The ICD-10-based comorbidity measures added little predictive value to the models for each of the outcomes of interest (EQ-5D index, EQ VAS, pain VAS, and satisfaction VAS). Charnley classification and the preoperative scores were the strongest predictors of both measures of postoperative HRQoL, of postoperative pain, and postoperative satisfaction with outcomes from surgery. Of all the predictors considered, only the Charnley classification was associated with all outcomes, irrespective of the timeframe considered. For each of the outcomes considered, there was a gradual increase in the models' predictive power with the length of the timeframe considered for calculating the comorbidity measures.
  
  
  CONCLUSIONS
  For predicting outcomes 1 year after THA, we found that there was no added value in ICD-10-based comorbidity measures if patient Charnley classification and preoperative HRQoL and pain measures were known.
  
  
  METHODS
  Level III, therapeutic study.
authors.affiliation: Harris Orthopaedic Laboratory, Massachusetts General Hospital, 55 Fruit Street, GRJ 1125, Boston, MA, 02114, USA. megreene@partners.org.|Swedish Hip Arthroplasty Register, Gothenburg, Sweden. megreene@partners.org.|Department of Orthopaedics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden. megreene@partners.org.
authors.forename: Meridith E
authors.initials: ME
authors.lastname: Greene
authors.affiliation: Harris Orthopaedic Laboratory, Massachusetts General Hospital, 55 Fruit Street, GRJ 1125, Boston, MA, 02114, USA.|Swedish Hip Arthroplasty Register, Gothenburg, Sweden.|Department of Orthopaedics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Ola
authors.initials: O
authors.lastname: Rolfson
authors.affiliation: Swedish Hip Arthroplasty Register, Gothenburg, Sweden.|Department of Clinical Sciences at Danderyd Hospital, Karolinska Institute, Stockholm, Sweden.
authors.forename: Max
authors.initials: M
authors.lastname: Gordon
authors.affiliation: Swedish Hip Arthroplasty Register, Gothenburg, Sweden.|Department of Orthopaedics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Göran
authors.initials: G
authors.lastname: Garellick
authors.affiliation: Swedish Hip Arthroplasty Register, Gothenburg, Sweden.|Department of Orthopaedics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Szilard
authors.initials: S
authors.lastname: Nemes
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects; D015897:Comorbidity; D005260:Female; D006621:Hip Joint / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D010147:Pain Measurement; D010149:Postoperative Pain / Q000175:diagnosis / Q000209:etiology; D017060:Patient Satisfaction; D011237:Predictive Value of Tests; D011788:Quality of Life; D020127:Recovery of Function; D012042:Registries; D012189:Retrospective Studies; D012307:Risk Factors; D011795:Surveys and Questionnaires; D013548:Sweden; D013997:Time Factors; D016896:Treatment Outcome