title: Assessing health-related quality of life in COPD: comparing generic and disease-specific instruments with focus on comorbidities.
abstract: BACKGROUND
  Chronic Obstructive Pulmonary Disease (COPD) influences different aspects of patient's health-related quality of life (HRQL). While disease-specific HRQL instruments focus on symptoms and functional impairments, generic instruments cover a broader view on health. This study compares the generic EQ-5D-3 L and two disease-specific questionnaires (St.-George's Respiratory Questionnaire (SGRQ-C), COPD Assessment Test (CAT)) in a comprehensive spectrum of COPD disease grades with particular attention on comorbidities and assesses the discriminative abilities of these instruments.
  
  
  METHODS
  Using data from the baseline visit of the German COPD cohort COSYCONET, mean HRQL scores in different COPD grades were compared by linear regression models adjusting for age, sex, education, smoking status, BMI, and low vs. high number of comorbidities or a list of several self-reported comorbid conditions. Discriminative abilities of HRQL instruments to differentiate between COPD grades were assessed by standardized mean differences.
  
  
  RESULTS
  In 2,291 subjects in COPD GOLD grades 1-4 EQ-5D-3 L utility, EQ-5D VAS, SGRQ, and CAT were found able to discriminate between COPD grades, with some limitations for the EQ-5D utility in mild disease. Both generic and disease-specific HRQL instruments reflected the burden of comorbid conditions. The SGRQ showed the best discrimination between COPD grades and was less influenced by comorbidities, while EQ-5D utility put a higher weight on comorbid conditions. For all instruments, psychiatric disorders and peripheral artery disease showed the strongest negative associations with HRQL.
  
  
  CONCLUSIONS
  All HRQL instruments considered reflect considerable impairment of HRQL in COPD patients, worsening with increasing COPD grade and number of comorbidities. Findings may support clinical assessment, choice of HRQL instrument in future studies, and parameterization of decision-analytic models.
authors.affiliation: Institute of Health Economics and Health Care Management, Helmholtz Zentrum München GmbH - German Research Center for Environmental Health, Comprehensive Pneumology Center Munich (CPC-M), Member of the German Center for Lung Research (DZL), Ingolstädter Landstr. 1, 85764, Neuherberg, Germany. margarethe.wacker@helmholtz-muenchen.de.
authors.forename: Margarethe E
authors.initials: ME
authors.lastname: Wacker
authors.affiliation: Institute and Outpatient Clinic for Occupational, Social and Environmental Medicine, Ludwig-Maximilians-Universität München, Ziemssenstr. 1, 80336, Munich, Germany.
authors.forename: Rudolf A
authors.initials: RA
authors.lastname: Jörres
authors.affiliation: Institute for Biostatistics, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany.
authors.forename: Annika
authors.initials: A
authors.lastname: Karch
authors.affiliation: Department of Research & Education, CIRO, Hornerheide 1, 6085, NM, Horn, The Netherlands.
authors.forename: Sarah
authors.initials: S
authors.lastname: Wilke
authors.affiliation: Institute of Epidemiology I, Helmholtz Zentrum München GmbH - German Research Center for Environmental Health, Comprehensive Pneumology Center Munich (CPC-M), Member of the German Center for Lung Research (DZL), Ingolstädter Landstr. 1, 85764, Neuherberg, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Heinrich
authors.affiliation: Institute and Outpatient Clinic for Occupational, Social and Environmental Medicine, Ludwig-Maximilians-Universität München, Ziemssenstr. 1, 80336, Munich, Germany.|Institute of Epidemiology I, Helmholtz Zentrum München GmbH - German Research Center for Environmental Health, Comprehensive Pneumology Center Munich (CPC-M), Member of the German Center for Lung Research (DZL), Ingolstädter Landstr. 1, 85764, Neuherberg, Germany.|Institute of General Practice, University Hospital Klinikum rechts der Isar, Technische Universität München, Orleansstr. 47, 81667, Munich, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Karrasch
authors.affiliation: Institute for Biostatistics, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany.
authors.forename: Armin
authors.initials: A
authors.lastname: Koch
authors.affiliation: Institute of Epidemiology I, Helmholtz Zentrum München GmbH - German Research Center for Environmental Health, Comprehensive Pneumology Center Munich (CPC-M), Member of the German Center for Lung Research (DZL), Ingolstädter Landstr. 1, 85764, Neuherberg, Germany.
authors.forename: Holger
authors.initials: H
authors.lastname: Schulz
authors.affiliation: Pulmonary Research Institute at LungenClinic Grosshansdorf, Airway Research Center North (ARCN), Member of the German Center for Lung Research (DZL), Wöhrendamm 80, 22927, Grosshansdorf, Germany.
authors.forename: Henrik
authors.initials: H
authors.lastname: Watz
authors.affiliation: Institute of Health Economics and Health Care Management, Helmholtz Zentrum München GmbH - German Research Center for Environmental Health, Comprehensive Pneumology Center Munich (CPC-M), Member of the German Center for Lung Research (DZL), Ingolstädter Landstr. 1, 85764, Neuherberg, Germany.|Institute of Health Economics and Health Care Management, Munich Center of Health Sciences, Ludwig-Maximilians-Universität München, Ludwigstr. 28/RG, 80539, Munich, Germany.
authors.forename: Reiner
authors.initials: R
authors.lastname: Leidl
authors.affiliation: Department of Respiratory Medicine, University of Marburg, University Giessen and Marburg Lung Center (UGMLC), Member of the German Center for Lung Research (DZL), Baldingerstraße, 35043, Marburg, Germany.
authors.forename: Claus
authors.initials: C
authors.lastname: Vogelmeier
authors.affiliation: Institute of Health Economics and Health Care Management, Helmholtz Zentrum München GmbH - German Research Center for Environmental Health, Comprehensive Pneumology Center Munich (CPC-M), Member of the German Center for Lung Research (DZL), Ingolstädter Landstr. 1, 85764, Neuherberg, Germany.
authors.forename: Rolf
authors.initials: R
authors.lastname: Holle
mesh_terms: D000203:Activities of Daily Living / Q000523:psychology*; D000368:Aged; D015897:Comorbidity; D003430:Cross-Sectional Studies; D005260:Female; D005858:Germany / Q000453:epidemiology; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000453:epidemiology* / Q000523:psychology; D011788:Quality of Life; D012189:Retrospective Studies; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires
keywords: Chronic obstructive pulmonary disease; Cohort study; Comorbidity; Health-related quality of life; Questionnaires; Utility