In a final report from the National Kidney Foundation (NKF) and the American Society of Nephrology (ASN) Task Force, published in both the American Journal of Kidney Diseases and the Journal of the American Society of Nephrology, recommendations are presented for a race-free approach to eGFR equations. The authors clarified the problem relating to eGFR equations, evaluated approaches to address the use of race in the estimation of GFR, and developed recommendations. Five approaches for estimation of GFR were evaluated while considering six attributes of each approach. The authors recommend immediate implementation of the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine equation refit without the race variable in all US laboratories for adults; this does not include race in the calculation and reporting, does include diversity in its development, is immediately available, and has acceptable performance characteristics and potential consequences that do not impact any one group disproportionately. National efforts to facilitate increased, routine, and timely use of cystatin C are recommended, especially to confirm eGFR in adults who are at risk for, or who already have, CKD. The CKD-EPI eGFR-cystatin C and eGFR creatinine-cystatin C refit without the race variables should be adopted if ongoing evidence supports acceptable performance.
Impaired Tubular Secretion for Solutes in Advanced CKD Examined
Secretory clearances for many solutes are reduced more than the GFR in advanced CKD, according to a study published in the Journal of the American Society of Nephrology. Impaired secretion of these solutes might contribute to uremic symptoms as patients approach dialysis, the study authors suggest. To test the hypothesis that secretory clearance relative to GFR is reduced in patients approaching dialysis, they used metabolomic analysis to identify solutes in simultaneous urine and plasma samples from patients with CKD and an eGFR of 7±2mL/ min per 1.73 m2 and controls. Metabolomic analysis identified 39 secreted solutes with fractional clearance greater than 3.0 in controls. Fractional clearance values in patients with CKD were reduced on average to 65%±27% of those in controls. These values were significantly lower for 18 of 39 individual solutes and significantly higher for only one. Assays of the secreted anions phenylacetylglutamine, P-cresol sulfate, indoxyl sulfate, and hippurate confirmed variable impairment of secretory clearances in advanced CKD.
