title: Recalibration and validation of the Charlson comorbidity index in Korean incident hemodialysis patients.
abstract: BACKGROUND
  Weights assigned to comorbidities to predict mortality may vary based on the type of index disease and advances in the management of comorbidities. We aimed to develop a modified Charlson comorbidity index (CCI) in incident hemodialysis patients (mCCI-IHD), thereby improving risk stratification for mortality.
  
  
  METHODS
  Data on 24,738 Koreans who received their first hemodialysis treatment between 2005 and 2008 were obtained from the Korean Health Insurance dataset. The mCCI-IHD score were calculated by summing up the weights which were assigned to individual comorbidities according to their relative prognostic significance determined by multivariate Cox proportional hazards model. The modified index was validated in an independent nationwide prospective cohort (n=1,100).
  
  
  RESULTS
  The Cox proportional hazards model revealed that all comorbidities in the CCI except ulcers significantly predicted mortality. Thus, the mCCI-IHD included 14 comorbidities with re-assigned severity weights. In the validation cohort, both the CCI and the mCCI-IHD were correlated with mortality. However, the mCCI-IHD showed modest but significant increases in c statistics compared with the CCI at 6 months and 1 year. The analyses using continuous net reclassification improvement revealed that the mCCI-IHD improved net mortality risk reclassification by 24.6% (95% CI, 2.5-46.7; P=0.03), 26.2% (95% CI, 1.0-51.4; P=0.04) and 42.8% (95% CI, 4.9-80.8; P=0.03) with respect to the CCI at 6 months and 1 and 2 years, respectively.
  
  
  CONCLUSIONS
  The mCCI-IHD facilitates better risk stratification for mortality in incident hemodialysis patients compared with the CCI, suggesting that it may be a preferred index for use in clinical practice and the statistical analysis of epidemiological studies.
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Jae Yoon
authors.initials: JY
authors.lastname: Park
authors.affiliation: Department of Dental Hygiene, College of Health Science, Eulji University, Gyeonggi-do, Korea.
authors.forename: Myoung-Hee
authors.initials: MH
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Seung Seok
authors.initials: SS
authors.lastname: Han
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Hyunjeong
authors.initials: H
authors.lastname: Cho
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Seoul National University, Seoul, Korea.
authors.forename: Ho
authors.initials: H
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine and Ewha Medical Research Institute, School of Medicine, Ewha Womans University, Seoul, Korea.
authors.forename: Dong-Ryeol
authors.initials: DR
authors.lastname: Ryu
authors.affiliation: Department of Internal Medicine, Wonkwang University College of Medicine Sanbon Hospital, Gyeonggi-do, Korea.
authors.forename: Hyunwook
authors.initials: H
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Hajeong
authors.initials: H
authors.lastname: Lee
authors.affiliation: Department of Internal Medicine, Seoul National University Boramae Medical Center, Seoul, Korea.
authors.forename: Jung Pyo
authors.initials: JP
authors.lastname: Lee
authors.affiliation: Department of Internal Medicine, Seoul National University Boramae Medical Center, Seoul, Korea.
authors.forename: Chun-Soo
authors.initials: CS
authors.lastname: Lim
authors.affiliation: Department of Public Health, Graduate School, Korea University, Seoul, Korea.
authors.forename: Kyoung Hoon
authors.initials: KH
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Kwon Wook
authors.initials: KW
authors.lastname: Joo
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Yon Su
authors.initials: YS
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Dong Ki
authors.initials: DK
authors.lastname: Kim
mesh_terms: D002138:Calibration; D015331:Cohort Studies; D015897:Comorbidity; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D006435:Renal Dialysis / Q000401:mortality; D015203:Reproducibility of Results; D056910:Republic of Korea; D012720:Severity of Illness Index; D013997:Time Factors