PHILADELPHIA –
The two alternative formulas for calculating eGFR, the CKiD U25 (Chronic Kidney Disease in Children under 25) and the European Kidney Function Consortium equations, showed higher levels of bias that resulted in underestimates of kidney function, particularly in younger adults 18-25 years old and in those with higher eGFR values, Leslie A. Inker, MD, said at Kidney Week 2023, organized by the American Society of Nephrology.
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Dr. Leslie A. Inker
However, for young adults with a history of childhood CKD and especially for those who continue under the care of pediatric clinicians even after they become young adults, use of the CKiD U25 equation, remains a reasonable option, said Dr. Inker, professor and director of the Kidney and Blood Pressure Center at Tufts Medical Center in Boston. The CKiD U25 equation is intended for people aged 1-25 years and came out in late 2020.
Pediatric nephrologists use the CKiD U25 but the results of the 2021 CKD-EPI race-free equation is what U.S. clinical labs routinely report for people aged 18 or older. “Our findings support the current practice of pediatric nephrologists” who may opt to use the CKiD U25 even when a patient turns 18 years or older, Dr. Inker said in an interview.
But the new results also support the current practice of U.S. labs, which is to focus on calculating eGFR in anyone at least 18 years old using the 2021 equation developed by the CKD-EPI, work led by Dr. Inker. The new findings confirm routine use of the 2021 CKD-EPI equation in adults as young as 18 years old, especially when they’re having their eGFR calculated for the first time, she said.
Discontinuity changing from CKiD U25 to CKD-EPI is ‘not huge’
“It’s important to understand that the 2021 CKD-EPI equation works in young adults,” noted Josef Coresh, MD, PhD, professor of clinical epidemiology at Johns Hopkins University, Baltimore, who collaborated on both the current study and on developing the 2021 CKD-EPI equation.
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Dr. Josef Coresh
The new data show that the discontinuity in eGFR produced by switching from the CKiD U25 formula to the 2021 CKD-EPI formula “is not huge, maybe about 5 mL/min per 1.73 m2 higher. People should focus on the new baseline and subsequent trends, not the modest difference between equations,” Dr. Coresh advised in an interview.
The study run by Dr. Inker and her associates used 1,491 people aged 18-40 years and enrolled in a cohort created by the CKD-EPI. They compared measured GFR levels in each subject with the estimates generated by the 2021 race-free CKD-EPI equation, the CKiD U25 equation, and a third equation developed by the EKFC and introduced in 2021.