Assessment of the new CKD-EPI equation to estimating glomerular filtration rate

Introduction: A recent report by the CKD-EPI Chronic Kidney Disease Epidemiology Collaboration) group describes a new equation to estimate the glomerular filtration rate (GFR). This equation has been developed from a population of 8,254 subjects who had the GFR measured by iothalamate clearance (mean 68 ml/min/1.73 m(2), SD 40 ml/min/1.73 m(2)). It includes variables such as serum creatinine, age, sex and race with different formula according to race, sex and creatinine value. The CKD-EPI equation improved the accuracy and precision results of the current first-choice MDRD-IDMS (Modification of Diet in Renal Disease-Isotopic Dilution Mass Spectrometry) formula, specially for GFR >60 ml/min/1.73 m(2) in a group of 3,896 subjects. Methods: The goal of our study was to compare the estimated GFR by using the new equation CKD-EPI with MDRD-IDMS in a wide cohort of 14,427 patients (5,234 women and 9,193 men), and to analyze the impact of the new CKD-EPI formula on the staging of patients with CKD. Results: Mean estimated GFR was 0.6 ml/min/1.73 m(2) higher with CKD-EPI as compared to MDRD-IDMS for the whole group, 1.9 ml/min/1.73 m(2) higher for women and 0.2 ml/min/1.73 m(2) lower for men. The percentage of CKD staging concordancy between equations varied from 79.4 % for stage 3A and 98.6% for stage 5. For those patients younger than 70 years, 18.9 % and 24 % MDRD-IDMS stages 38 and 3A were reclasified as CKD 3A and 2 by CKD-EPI, respectively. For the same stages in the group younger than 70 years, the percentage of reclasified patients increased up to 34.4% and 33.4%, respectively. Conclusion: The new CKD-EPI equation to estimate the GFR reclasifies an important number of patients to higher CKD stages (higher GFR), specially younger women, clasified as CKD stage 3 by MDRD-IDMS.