Predicting mortality in older adults with kidney disease: a pragmatic prediction model

Abstract

Objectives: To develop mortality risk prediction models for older adults with chronic kidney disease (CKD) that include comorbidities and measures of health status and use not associated with particular comorbid conditions (nondisease-specific measures).

Design: Retrospective cohort study.

Setting: Kaiser Permanente Northwest (KPNW) Health Maintenance Organization.

Participants: Individuals with severe CKD (estimated glomerular filtration rate<30 mL/min per 1.73 m2; N=4,054; n=1,915 aged 65-79, n=2,139 aged ≥80) who received care at KPNW between 2000 and 2008.

Measurements: Cox proportional hazards analysis was used to examine the association between selected participant characteristics and all-cause mortality and to generate age group-specific risk prediction models. Predicted and observed risks were evaluated according to quintile. Predictors from the Cox models were translated into a points-based system. Internal validation was used to provide best estimates of how these models might perform in an external population.

Results: The risk prediction models used 16 characteristics to identify participants with the highest risk of mortality at 2 years for adults aged 65 to 79 and 80 and older. Predicted and observed risks agreed within 5% for each quintile; a 4 to 5 times difference in 2-year predicted mortality risk was observed between the highest and lowest quintiles. The c-statistics for each model (0.68-0.69) indicated effective discrimination without evidence of significant overfit (slope shrinkage 0.06-0.09). Models for each age group performed similarly for mortality prediction at 6 months and 2 years in terms of discrimination and calibration.

Conclusion: When validated, these risk prediction models may be helpful in supporting discussions about prognosis and treatment decisions sensitive to prognosis in older adults with CKD in real-world clinical settings.

Keywords: chronic kidney disease; elderly; mortality; risk.

Figure 1

Flowchart for cohort development. KPNW = Kaiser Permanente Northwest Health Maintenance Organization. eGFR = estimated glomerular filtration rate.

Figure 2

Kaplan-Meier failure plots of prediction models for ages 65-79 (top) and >80 (bottom). This Kaplan-Meier failure curve shows the observed risk (solid lines) and predicted risk (dotted lines) of mortality according to quintiles of predicted risk based on the risk score.The vertical line demarcates 6 months, whereas the overall plot ends at 24 months (2 years).