Staging chronic kidney disease and estimating glomerular filtration rate: an opinion paper about the new international recommendations

In January 2013, the international recommendations of the KDIGO (for “Kidney Disease: Improving Global Outcomes”) to define chronic kidney disease (CKD) and classify patients in CKD stages have been published. In this opinion article, we will review and discuss the most important guidelines proposed about CKD staging and glomerular filtration rate (GFR) estimating. In particular, we question the choice of fixed knot values at 60 mL/min/1.73 m² to define CKD. We also question the strategies proposed to measure and use cystatin C results.