In this issue of AJKD, Rath et al1 explored the differences in the incidence and prognosis among patients diagnosed with stage 4 chronic kidney disease (CKD G4) using 4 distinct algorithms: (1) a single estimated glomerular filtration rate (eGFR) 15-29mL/min/1.73m2 (single test); (2) a 2-test sequence with the first eGFR90 days apart (where measurements in between these 2 could be eGFR>30mL/min/1.73m2)(2 tests); (3) 2 or more eGFR measurements90 days (qualifying period) with the last eGFR in the qualifying period between 15 and 29mL/min/1.73m2 (relaxed sustained); and (4) 2 or more consecutive measurements between 15 and 29mL/min/1.73m2 sustained for>90 days (rigorous sustained).