Validation of the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation in advanced chronic renal failure.

INTRODUCTION: The aim of this work was to study the accuracy of the CKD-EPI equation to estimate the glomerular filtrate in patients with advanced chronic renal failure.

OBJECTIVE: We compared the estimations of Modification of Diet in Renal Disease (MDRD), Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and Cockcroft-Gault (CG) equations to a glomerular filtration rate measured as the arithmetic mean of the urea and creatinine clearances (ClUrCr).

MATERIAL AND METHODS: The study was made in 89 nondialyzed patients with chronic renal disease in stage 4 or 5. Serum creatinine values were recalibrated to standardized creatinine measurements. In each patient, the difference between each estimating equation and the measured glomerular filtration rate was calculated. The absolute difference expressed as a percentage of the measured glomerular filtration rate indicates the intermethod variability.

RESULTS: Overall, the glomerular filtration rate measured as the ClUrCr was 14.5 ± 5.5 ml/min/1.73 m(2); and the results of the estimating equations were: MDRD 14.3 ± 5.5 (p = NS); CKD-EPI 13.6 ± 5.4 (p <0.01) and CG 16.8 ± 6.5 ml/min/1.73 m(2) (p <0.001). The variability of the estimating equations was 16 ± 12.2%, 16.7 ± 12,1% and 22 ± 15.6% (p <0.05), for MDRD, CKD-EPI and CG. The percentage of estimates within 30% above or below the measured glomerular filtration rate was 85% for MDRD, 88% for CKD-EPI and 70% for CG. The CG variability, but not MDRD variability or CKD-EPI variability, was influenced by gender (19.3 ± 15.1% in males vs 27.3 ± 15.5% in females, p <0.05) and showed a negative correlation with the glomerular filtration rate (r = -0.23, p <0.05) and the age (r = -0.24, p <0.05) and positive correlation with the body mass index (r = 0.37, p <0.001). In patients with chronic renal disease in stage 5, the variability of the different estimating equations was similar.

CONCLUSIONS: We conclude that in our population with advanced chronic renal failure, the CKD-EPI equation is as accuracy as the MDRD equation. With standardized creatinine the CG equation has a lower accuracy and its utilization may be reconsiderated.