New Clinical Index May Help Predict Mortality in Patients With End-Stage Renal Disease

Laurie Barclay, MD

April 07, 2010

April 7, 2010 — A new clinical prediction index may help evaluate the risk for mortality in patients with end-stage renal disease (ESRD) considering transplantation, according to the results of a study reported online March 29 in the Canadian Medical Association Journal.

"We aimed to derive and validate a new index to quantify survival accurately for the various treatment options facing a patient with ...ESRD," write Carl van Walraven, MD, MSc, from the University of Ottawa in Ontario, Canada, and colleagues. "We based this prognostic index on readily available data, so that it could be easily implemented in the clinical setting when transplantation-related counseling takes place. We modified this model into a simple scoring system to quantify survival without transplantation, with deceased-donor transplantation or with living-donor transplantation."

Using a population of 169,393 patients with ESRD who were eligible for transplantation, the investigators derived and validated a multivariable survival model predicting time to death, and they modified the model into a simple point-system index.

Nearly one quarter (23.5%) of the cohort died. There were 12 variables identified as independent predictors of mortality: age, race, cause of renal failure, body mass index (BMI), comorbid disease, smoking status, employment, serum albumin level, year of first renal replacement therapy, kidney transplantation, time to transplant wait-listing, and time on the wait list.

With use of the index, patients were separated into 26 groups with significantly varying 5-year survival duration, ranging from 97.8% in the lowest-risk group to 24.7% in the highest-risk group. Concordance probability of the index score in the validation group was 0.746 (95% confidence interval, 0.741 - 0.75), suggesting that it was highly discriminative. For each level of index score, observed survival duration in the derivation and validation cohorts was similar in 93.9% of patients.

"Our prognostic index uses commonly available information to predict mortality accurately in patients with ...ESRD," the study authors write. "This index could provide valuable quantitative data on survival for clinicians and patients to use when deciding whether to pursue transplantation or remain on dialysis."

Limitations of this study include lack of generalizability beyond patients who are considered to be candidates for renal transplantation, the need to update the prognostic index occasionally when new data become available, and lack of donor characteristics (other than living or deceased) in the model.

"Finally, information on comorbidities in the United States Renal Data System may be incompletely captured, and only the presence — not the severity — of the illness is accounted for in the model," the study authors conclude. "Hence, the impact of some comorbidities on survival may be underestimated by our model. Prospective validation of the model would help determine if this underestimation is indeed happening."

This study received no external funding. The study authors have disclosed no relevant financial relationships.

CMAJ. Published online March 29, 2010. Abstract