An alternative classification system to determine severity of chronic kidney disease (CKD), using both estimated glomerular filtration rate (eGFR) and proteinuria, has been compared with the NKF–KDOQI system that primarily uses eGFR. Inker et al. compared these systems in participants of NHANES with and without various complications. They found that participants without the complications were more likely to be reclassified more appropriately to lower CKD stages using the alternative system, whereas the NKF–KDOQI system better classified patients with concurrent CKD complications.