Background: Patients with chronic kidney disease (CKD) stages 3-5 are at increased risk of progressing to end-stage renal disease (ESRD) or dying prior to the development of ESRD compared with patients with less severe CKD. The magnitude of these risks may vary by stage, which has important implications for therapy. Our objective was to apply a competing risk analysis in order to estimate these risks in a referred cohort of patients with CKD by stage at referral and identify risk factors associated with each outcome.

Study design: Retrospective cohort study.

Setting & participants: 3,273 patients with CKD stages 3-5 who were referred to the nephrology clinic at Sunnybrook Health Sciences Centre, Toronto, prior to December 31, 2008, with follow-up data available prior to December 31,2008.

Predictors: CKD stage at time of referral; demographic, laboratory, and clinical characteristics.

Outcomes: ESRD, defined as the initiation of dialysis therapy or pre-emptive kidney transplantation, and death from any cause prior to ESRD.

Measurements: Baseline laboratory data.

Results: Over a median follow-up of 2.98 years, 459 patients (14%) developed ESRD and 540 (16%) died. Rates per 100 patient-years of ESRD versus death prior to ESRD for CKD stage 3A were 0.6 (95% CI, 0.1-1.0) versus 2.2 (95% CI, 1.2-3.1; P<0.001); for CKD stage 3B, 1.4 (95% CI, 0.8-2.1) versus 4.4 (95% CI, 3.3-5.6; P<0.001); for CKD stage 4, 7.7 (95% CI, 5.9-9.4) versus 8.0 (95% CI, 6.2-9.8; P=0.6); and for CKD stage 5, 41.4 (95% CI, 34.4-48.4) versus 9.4 (95% CI, 5.2-13.4; P<0.001). For those with CKD stage 4, we identified 12 variables associated with higher risk of ESRD and 7 variables associated with higher risk of death prior to ESRD.

Limitations: A cohort analyzed retrospectively.

Conclusions: ESRD and death prior to ESRD incidence was most similar in CKD stage 4. We identified variables easily assessed at the time of referral that could discriminate between these risks.