Switching from the current KDIGO classification system to an age-adapted CKD classification system increases CKD prevalence among younger adults and decreases it among older adults in the United States. Investigators reported the paradigm-shifting findings at Kidney Week 2022, the annual meeting of the American Society of Nephrology.

Under current KDIGO guidelines, CKD is defined as an estimated glomerular filtration rate (eGFR) less than 60 mL/min/1.73 m2 based on the race-free 2021 CKD-EPI equation or a urinary albumin-to-creatinine ratio (UACR) of 30 mg/g or more. Among the 31.1 million individuals in the United States who have CKD according to the KDIGO definition, 39.4% are aged 18 to less than 40 years, 43.4% are aged 40-65 years, and 17.2% are older than 65 years. Under KDIGO, the median age skews older at each CKD stage: 71 years for G3A, 76 years for G3B, 78 years for G4, and 63 years for G5. The investigators used 2017-2020 data from 8016 participants in the National Health and Nutrition Examination Survey (NHANES).

Under an age-adapted CKD classification system, CKD is defined as an eGFR less than 75 mL/min/1.73m2 for adults aged 18 to less than 40 years, less than 60 mL/min/1.73 m2 for those aged 40 to 65 years, or less than 45 mL/min/1.73 m2 for those older than 65 years, or a UACR of 30 mg/g or more, Kamyar Kalantar-Zadeh, MD, PhD, of the University of California Irvine, reported for his team. The age-adapted classification takes into account physiological age-related decline in GFR. For each age group, the respective eGFR threshold indicates the point at which mortality risk increases. 

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Using the CKD-Age classification, 5.2 million (16.7%) of those with CKD under KDIGO criteria were reclassified to having no CKD, Dr Kalantar-Zadeh reported. Another 1.2 million (0.6%) of those without CKD under KDIGO were reclassified to having CKD using the age-adjusted definitions.

“I believe that KDIGO classifications of CKD and its stages should be abandoned in real-world patient care,” Dr Kalantar-Zadeh said in an interview with Renal & Urology News. “Age-based CKD classification may prevent overdiagnosis of CKD in older individuals and identify younger individuals with low eGFR at risk for kidney failure, allowing prioritization of care.”

He added that the CKD-EPI equations promoted by KDIGO should not replace the Cockcroft-Gault equation for drug dosing of chemotherapy, antibiotics, and other medications, given probable errors that may have serious consequences for patient safety.

Dr Kalantar-Zadeh acknowledged that US CKD prevalence will likely change substantially once GFR is accurately measured rather than estimated. 


Tio MC, Syed, Aliba, Streja E, et al. Changes in CKD prevalence in the United States using the age-adapted CKD classification system. Presented at: Kidney Week; November 3-6, 2022. Abstract: FR-OR24.

Delanaye P, Jager KJ, Bökenkamp A, et al. CKD: A call for an age-adapted definition. J Am Soc Nephrol. 2019 Oct;30(10):1785-1805. doi:10.1681/ASN.2019030238