Predictive performance of the new race-free Chronic Kidney Disease Epidemiology Collaboration equations for kidney outcome in Korean patients with chronic kidney disease

BACKGROUND: The new Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations without a race coefficient have gained recognition across the United States. We aimed to test whether these new equations performed well in Korean patients with chronic kidney disease (CKD). METHODS: This study included 2,149 patients with CKD G1–G5 without kidney replacement therapy from the Korean Cohort Study for Outcome in Patients with CKD (KNOW-CKD). The estimated glomerular filtration rate (eGFR) was calculated using the new CKD-EPI equations with serum creatinine and cystatin C. The primary outcome was 5-year risk of kidney failure with replacement therapy (KFRT). RESULTS: When we adopted the new creatinine equation [eGFR(cr) (NEW)], 81 patients (23.1%) with CKD G3a based on the current creatinine equation (eGFR(cr)) were reclassified as CKD G2. Accordingly, the number of patients with eGFR of <60 mL/min/1.73 m(2) decreased from 1,393 (64.8%) to 1,312 (61.1%). The time-dependent area under the receiver operating characteristic curve for 5-year KFRT risk was comparable between the eGFR(cr) (NEW) (0.941; 95% confidence interval [CI], 0.922–0.960) and eGFR(cr) (0.941; 95% CI, 0.922–0.961). The eGFR(cr) (NEW) showed slightly better discrimination and reclassification than the eGFR(cr). However, the new creatinine and cystatin C equation [eGFR(cr-cys) (NEW)] performed similarly to the current creatinine and cystatin C equation. Furthermore, eGFR(cr-cys) (NEW) did not show better performance for KFRT risk than eGFR(cr) (NEW). CONCLUSION: Both the current and the new CKD-EPI equations showed excellent predictive performance for 5-year KFRT risk in Korean patients with CKD. These new equations need to be further tested for other clinical outcomes in Koreans.