Validation of the Kidney Failure Risk Equation in Manitoba

BACKGROUND Patients with chronic kidney disease (CKD) are at risk to progress to kidney failure. We previously developed the Kidney Failure Risk Equation (KFRE) to predict progression to kidney failure in patients referred to nephrologists. OBJECTIVE The objective of this study was to determine the ability of the KFRE to discriminate which patients will progress to kidney failure in an unreferred population. DESIGN A retrospective cohort study was conducted using administrative databases. SETTING This study took place in Manitoba, Canada. MEASUREMENTS Age, sex, estimated glomerular filtration rate (eGFR), and urine albumin-to-creatinine ratio (ACR) were measured. METHODS We included patients from the Diagnostic Services of Manitoba database with an eGFR <60 mL/min/1.73 m2 and ACR measured between October 2006 and March 2007. Five-year kidney failure risk was predicted using the 4-variable KFRE and compared with treated kidney failure events from the Manitoba Renal Program database. Sensitivity and specificity for KFRE risk thresholds (3% and 10% over 5 years) were compared with eGFR thresholds (30 and 45 mL/min/1.73 m2). RESULTS Of 1512 included patients, 151 developed kidney failure over the 5-year follow-up period. The 4-variable KFRE showed a superior prognostic discrimination compared with eGFR alone (area under the receiver operating characteristic curve [AUROC] values, 0.90 [95% confidence interval {CI}: 0.88-0.92] for KFRE vs 0.78 [95% CI: 0.74-0.83] for eGFR). At a 3% threshold over 5 years, the KFRE had a sensitivity of 97% and a specificity of 62%. At 10% risk, sensitivity was 86%, and specificity was 80%. LIMITATIONS Only 11.7% of stage 3-5 CKD patients had simultaneous ACR measurement. The KFRE does not account for other indications for referral such as suspected glomerulonephritis, polycystic kidney disease, and recurrent stone disease. CONCLUSIONS The KFRE has been validated in a population with a demographic and referral profile heretofore untested and performs well at predicting 5-year risk of kidney failure in a population-based sample of Manitobans with CKD stages 3 to 5. Thresholds of 3% and 10% over 5 years are sensitive, specific, and can be used in clinical decision making. Further testing of the 4-variable KFRE and these thresholds in clinical practice should be considered.