Low renal replacement therapy incidence among slowly progressing elderly chronic kidney disease patients referred to nephrology care: an observational study

Abstract

Background: Elderly patients with advanced chronic kidney disease (CKD) have a high risk of death before reaching end-stage kidney disease. In order to allocate resources, such as advanced care nephrology where it is most needed, it is essential to know which patients have the highest absolute risk of advancing to renal replacement therapy (RRT).

Methods: We included all nephrology-referred CKD stage 3b-5 patients in Sweden 2005-2011 included in the Swedish renal registry (SRR-CKD) who had at least two serum creatinine measurements one year apart (+/- 6 months). We followed these patients to either initiation of RRT, death, or September 30, 2013. Decline in estimated glomerular filtration rate (eGFR) (%) was estimated during the one-year baseline period. The patients in the highest tertile of progression (>18.7% decline in eGFR) during the initial year of follow-up were classified as "fast progressors". We estimated the cumulative incidence of RRT and death before RRT by age, eGFR and progression status using competing risk models.

Results: There were 2119 RRT initiations (24.2%) and 2060 deaths (23.5%) before RRT started. The median progression rate estimated during the initial year was -8.8% (Interquartile range [IQR] - 24.5-6.5%). A fast initial progression rate was associated with a higher risk of RRT initiation (Sub Hazard Ratio [SHR] 2.24 (95% confidence interval [CI] 2.00-2.51) and also a higher risk of death before RRT initiation (SHR 1.27 (95% CI 1.13-1.43). The five year probability of RRT was highest in younger patients (<65 years) with fast initial progression rate (51% in CKD stage 4 and 76% in stage 5), low overall in patients >75 years with a slow progression rate (7, 13, and 25% for CKD stages 3b, 4 and 5 respectively), and slightly higher in elderly patients with a fast initial progression rate (28% in CKD stage 4 and 47% in CKD stage 5) or with diabetic kidney disease.

Conclusions: The 5-year probability of RRT was low among referred slowly progressing CKD patients >75 years of age because of the competing risk of death.

Keywords: Chronic Kidney Disease; End-stage kidney disease; Epidemiology; Estimated glomerular filtration rate; Mortality; Progression rate; Renal replacement therapy.

Fig. 1

Patient’s inclusion flow chart. RRT (renal replacement therapy), eGFR (estimated glomerular filtration rate), N (number), CKD (chronic kidney disease)

Fig. 2

Cumulative incidence function for renal replacement therapy (blue) and death before renal replacement therapy (orange) by age, chronic kidney disease stage, and disease progression rate for patients under nephrology care. The cumulative incidence function was adjusted for the remaining covariates using their median value if numeric or most frequent value if categorical. On the Y-axis is cumulative incidence stratified by three CKD stages. On the X-axis is the time from inclusion in years, stratified by age category and progression status after the initial baseline period

Fig. 3

Five-year cause-specific probabilities of renal replacement therapy and death before renal replacement therapy for hypertensive kidney disease patients with a fast and slow progression rate stratified by age and chronic kidney disease stage. CKD (chronic kidney disease) categorized according to KDIGO classification system

Fig. 4

Contribution of each competing event (renal replacement therapy and death) to the overall risk of an event at any time during follow-up. The area represents the contribution of each competing event to the overall risk of event at any time. The dashed horizontal line at 50% is the equivalence of contributions line