(a) KDIGO CKD stage classification for the ASPREE cohort participants by CKD-EPIeGFR (left panel) and BIS1 (right panel). (b) Percentage of participants in each CKD-EPI CKD stage reclassified to a new stage by BIS1eGFR. Reclassified down corresponds to reclassification to a higher (i.e. more severe) CKD G stage, for example from stage G1 to G2. Reclassified up corresponds to reclassification to a lower (i.e. less severe) CKD G stage, for example from stage G4 to G3b. BIS1, Berlin Initiative Study; CKD-EPI, Chronic Kidney Disease Epidemiology Collaboration; eGFR, estimated glomerular filtration rate; UACR, urine albumin-to-creatinine ratio.