Clinical Epidemiology (Jan 2021)

Adaptation of the Charlson Comorbidity Index for Register-Based Research in Sweden

  • Ludvigsson JF,
  • Appelros P,
  • Askling J,
  • Byberg L,
  • Carrero JJ,
  • Ekström AM,
  • Ekström M,
  • Smedby KE,
  • Hagström H,
  • James S,
  • Järvholm B,
  • Michaelsson K,
  • Pedersen NL,
  • Sundelin H,
  • Sundquist K,
  • Sundström J

Journal volume & issue
Vol. Volume 13
pp. 21 – 41

Abstract

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Jonas F Ludvigsson,1– 4 Peter Appelros,5 Johan Askling,6,7 Liisa Byberg,8 Juan-Jesus Carrero,1 Anna Mia Ekström,9,10 Magnus Ekström,11 Karin Ekström Smedby,6 Hannes Hagström,12– 14 Stefan James,15,16 Bengt Järvholm,17 Karl Michaelsson,8 Nancy L Pedersen,18 Helene Sundelin,19,20 Kristina Sundquist,21 Johan Sundström22– 24 1Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden; 2Department of Pediatrics, Orebro University Hospital, Orebro, Sweden; 3Division of Epidemiology and Public Health, School of Medicine, University of Nottingham, Nottingham, UK; 4Department of Medicine, Columbia University College of Physicians and Surgeons, New York, New York, USA; 5University Health Care Research Center, Faculty of Medicine and Health, Örebro University, Örebro SE-701 82, Sweden; 6Clinical Epidemiology Division, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden; 7Rheumatology, Theme Inflammation and Infection, Karolinska University Hospital, Stockholm, Sweden; 8Department of Surgical Sciences, Uppsala University, Uppsala, Sweden; 9Global & Sexual Health Research Group (GloSH), Department of Global Public Health, Karolinska Institutet, Stockholm, Sweden; 10Faculty of Medicine, Department of Clinical Sciences Lund, Respiratory Medicine and Allergology, Lund University, Lund, Sweden; 11Department of Infectious Diseases, Karolinska University Hospital, Stockholm, Sweden; 12Division of Hepatology, Department of Upper GI Diseases, Karolinska University Hospital, Stockholm, Sweden; 13Clinical Epidemiology Division, Department of Medicine, Solna, Karolinska Institutet, Stockholm, Sweden; 14Department of Medicine, Karolinska Huddinge, Institutet, Stockholm, Sweden; 15Department of Medical Sciences, Cardiology, Uppsala University, Uppsala, Sweden; 16Uppsala Clinical Research Center, Uppsala University, Uppsala, Sweden; 17Department of Public Health and Clinical Medicine, Umeå University, Umeå, Sweden; 18Department of Medical Epidemiology, Karolinska Institutet, Stockholm, Sweden; 19Neuropediatric Unit, Department of Women’s and Children’s Health, Karolinska University Hospital, Karolinska Institutet, Stockholm, Sweden; 20Division of Children’s and Women’s Health, Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden; 21Center for Primary Health Care Research, Department of Clinical Sciences, Malmö, Lund University, Lund, Sweden; 22Department of Medical Sciences, Uppsala University, Uppsala, Sweden; 23The George Institute for Global Health, University of New South Wales, Sydney, Australia; 24Department of Family Medicine and Community Health, Department of Population Health Science and Policy, Icahn School of Medicine at Mount Sinai, New York, NY, USA; 25Center for Community-Based Healthcare Research and Education (CoHRE), Department of Functional Pathology, School of Medicine, Shimane University, JapanCorrespondence: Jonas F LudvigssonDepartment of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm 17177, SwedenEmail [email protected]: Comorbidity indices are often used to measure comorbidities in register-based research. We aimed to adapt the Charlson comorbidity index (CCI) to a Swedish setting.Methods: Four versions of the CCI were compared and evaluated by disease-specific experts.Results: We created a cohesive coding system for CCI to 1) harmonize the content between different international classification of disease codes (ICD-7,8,9,10), 2) delete incorrect codes, 3) enhance the distinction between mild, moderate or severe disease (and between diabetes with and without end-organ damage), 4) minimize duplication of codes, and 5) briefly explain the meaning of individual codes in writing.Conclusion: This work may provide an integrated and efficient coding algorithm for CCI to be used in medical register-based research in Sweden.Keywords: Charlson comorbidity score, comorbidity, disease, epidemiology, public health, Sweden

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