Predicting chronic kidney disease outcomes: are two estimated glomerular filtration rates better than one?

The National Kidney Foundation's (NKF) Kidney Disease Outcomes Quality Initiative (KDOQI) definition of chronic kidney disease (CKD), stages 3-5, requires 2 estimated glomerular filtration rates (eGFRs) <60 ml/min/1.73 m(2) more than 3 months apart. By requiring 2 eGFRs, the NKF definition reduced identification of people without chronic disease, which may have decreased identification of individuals with early CKD, but increased identification of those who ultimately have progression of CKD or require renal replacement therapy (RRT). Our objective was to determine whether 2 eGFR tests were better than 1 eGFR as a predictor of RRT, CKD progression, or death. This retrospective incident cohort study evaluates outcomes in adults with an initial eGFR <60 ml/min/1.73 m(2) and a second eGFR after 90 days by examining a third follow-up eGFR. For the 2086 patients in this study, the mean initial eGFR was 50.7 ml/min/1.73 m(2) and the mean second eGFR was 59.3 ml/min/1.73 m(2). More than 40% of the population (925) did not have CKD based upon their second eGFR. The initial eGFR was the best predictor of the third eGFR. There was no material difference in the ability to predict outcome measures between 1 versus 2 eGFR tests, regardless of eGFR value or associated comorbidities. Identifying patients with CKD is a critical step when beginning to implement population management strategies for those patients. Our findings illustrate some of the trade-offs in strategies inherent in methods that might be used to identify patients with CKD; 1 eGFR will identify patients about 5 months sooner, allowing additional time for nephrologist and other therapeutic intervention, but approximately doubles the population to be managed.