Comorbidity burden at dialysis initiation and mortality: A cohort study.
BACKGROUND
A high level of comorbidity at dialysis initiation is associated with an increased risk of death. However, contemporary assessments of the validity and prognostic value of comorbidity indices are lacking.


OBJECTIVE
To assess the validity of two comorbidity indices and to determine if a high degree of comorbidity is associated with mortality among dialysis patients.


METHODS
Cohort study.


METHODS
QEII Health Sciences Centre (Halifax, Nova Scotia, Canada).


METHODS
Incident, chronic dialysis patients between 01 Jan 2006 and 01 Jul 2013.


METHODS



METHODS
The Charlson Comorbidity Index (CCI) and End-Stage Renal Disease Comorbidity Index (ESRD-CI) were used to classify individual comorbid conditions into an overall score. Comorbidities were classified using patient charts and electronic records.


RESULTS
All-cause mortality. Confounders: Patient demographics, dialysis access, cause of ESRD and baseline laboratory data.


METHODS
Regression coefficients were estimated on the CCI and ESRD-CI. Discrimination for death was assessed using Harrell's c-index. Adjusted Cox proportional hazard models were used to calculate relative hazards and 95 % confidence intervals for each category of the CCI and ESRD-CI.


RESULTS
The cohort consisted of 771 ESRD patients from 01 Jan 2006 to 01 Jul 2013. Most were male (62 %) and Caucasian (91 %). The cohort had a high proportion of diabetes (48 %), history of previous myocardial infarction (31 %) and heart failure (22 %). Regression coefficients on the CCI and ESRD-CI were 0.55 and 0.52, respectively. The c-index, for the prediction of death, was 0.61 for the CCI and 0.63 for the ESRD-CI. ESRD-CI scores of 4, 5 and ≥6 were associated with a similar mortality risk (adjusted relative hazard of 1.95, 1.89 and 1.99, respectively). There was a small increased mortality risk for CCI scores of 4, 5 and ≥6 (adjusted relative hazard of 1.86, 2.38 and 2.71, respectively).


CONCLUSIONS
Classification of comorbidities for each patient was determined by clinical impression.


CONCLUSIONS
The CCI and ESRD-CI have a limited ability to discriminate mortality risk for incident dialysis patients. Acknowledging the frequency with which they are used, this study emphasizes the need to re-examine the usefulness of previously derived comorbidity indices in contemporary dialysis cohorts.
Faculty of Medicine, Dalhousie University, Halifax, NS Canada.
Alwyn T
AT
Gomez
Department of Medicine (Division of Nephrology), Dalhousie University, Halifax, NS Canada ; Nova Scotia Health Authority, 5820 University Avenue, Halifax, NS Canada B3H 1V8.
Bryce A
BA
Kiberd
MRC Clinical Trials unit at UCL, London, UK.
J Patrick
JP
Royston
Department of Medicine (Division of Nephrology), Dalhousie University, Halifax, NS Canada.
Talal
T
Alfaadhel
Department of Medicine (Division of Nephrology), Dalhousie University, Halifax, NS Canada ; Nova Scotia Health Authority, 5820 University Avenue, Halifax, NS Canada B3H 1V8.
Steven D
SD
Soroka
Department of Medicine, University of Calgary, Calgary, AB Canada ; Department of Community Health Sciences, University of Calgary, Calgary, AB Canada.
Brenda R
BR
Hemmelgarn
Department of Medicine (Division of Nephrology), Dalhousie University, Halifax, NS Canada ; Nova Scotia Health Authority, 5820 University Avenue, Halifax, NS Canada B3H 1V8.
Karthik K
KK
Tennankore