The widely used Kidney Failure Risk Equation (KFRE) overestimates the risk for kidney failure in patients with advanced chronic kidney disease (CKD) who are aged 80 years and older, a new study finds.
Investigators compared predicted vs actual kidney failure rates among 1701 patients at an advanced CKD clinic, of whom 30%, 24%, 27%, and 19% were aged younger than 60, 60-69, 70-79, and 80 years or older, respectively.
The KFRE overestimated the kidney failure risk over 2 and 5 years among the group 80 years and older with significant absolute and relative differences of 7.6% and 22.8%, respectively, over 2 years and 24.7% and 40.4%, respectively, over 5 years, Gregory L. Hundemer, MD, MPH, of The Ottawa Hospital in Ottawa, Ontario, Canada, and colleagues reported in Kidney International Reports. Overestimation was greatest for patients with the highest predicted risks for kidney failure.
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The KFRE had acceptable discrimination across age groups.
The 4-variable KFRE predicts a patient’s risk for kidney failure using age, sex, estimated glomerular filtration rate (eGFR) based on the CKD-EPI equation, and urine albumin-to-creatinine ratio (UACR). The equation treats death prior to kidney failure as a censoring event rather than a competing event.
“This overestimation in the risk of kidney failure by the KFRE relates to the magnified competing risk of death with older age and increases over longer time horizons,” Dr Hundemer’s team explained.
“Nephrologists should be aware of this limitation of the KFRE as it may impact advanced care planning for the elderly advanced CKD population.”
Older patients may die from other causes before they reach kidney failure, for example, and may opt to delay invasive procedures for dialysis.
A majority of patients (74%) in this study were White, so these results may not be generalizable to Black patients, who made up only 4% of the cohort, especially since the existing CKD-EPI equation uses a race coefficient.
Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.
Reference
Hundemer GL, Tangri N, Sood MM, et al. The effect of age on performance of the kidney failure risk equation in advanced CKD. Kidney Int Rep. Published online October 7, 2021. doi:10.1016/j.ekir.2021.09.006
