Diagnosis

Ping Liu, PhD, and Pietro Ravani, MD, PhD, on Chronic Kidney Disease and Age

It is estimated that 15% of all adults have chronic kidney disease (CKD), but the results of a recent study suggest that the prevalence of CKD in older adults may be overestimated.1

To better understand the impact of normal aging on the CKD disease burden, the researchers conducted a cohort study that compared the current, fixed threshold of estimated glomerular filtration rate (eGFR) with an age-adapted threshold.

To learn more about the study results, Consultant360 reached out to 2 of the study authors, Ping Liu, PhD, and Pietro Ravani, MD, PhD, both from the University of Calgary in Alberta, Canada.

Ping Liu was supported by post-doctoral fellowship from the Canadian Institutes of Health Research (Funding Reference Number MFE-152465). Pietro Ravani currently holds the Roy and Vi Baay Chair in Kidney Research at the University of Calgary.

 

Consultant360: What was the impetus for your study?

Ping Liu and Pietro Ravani: An age-calibrated definition of CKD has been proposed for at least a decade based on (1) evidence that eGFR physiologically declines with age, though to a variable degree within an age group, (2) observation that despite global population aging in the very elderly the demand for therapies for kidney failure has not increased, and (3) lack of data on absolute risk of kidney failure. While existing studies have compared the “speed” (rates or hazard rates) of CKD progression toward kidney failure by eGFR category, they never presented the absolute risk; instead, they compared relative speeds without providing estimates of the “journey” people completed over a certain period of time.

C360: Your study found that using the same eGFR criteria for all adults regardless of age may be overestimating the CKD burden in older adults. Is this a result that surprised you, or did you anticipate this?

PL and PR: We expected this result. Although the hypothesis that lower eGFR with older age is normal has never been tested properly, previous studies never estimated the absolute risk of kidney failure, which is very low (in the order of 1:1000 at 5 years) and becomes lower with advancing age (while the risk of death is hundreds of times higher).

C360: Are there any other aspects of the standard of care for managing CKD that currently account for age?

PL and PR: Nephrology care teams offer education about treatment options for kidney failure and notice that the elderly are more likely to forgo dialysis therapy and choose conservative, palliative care of kidney failure.

C360: What are some clinical pearls you would give your peers for diagnosing and managing CKD in older adults?

PL and PR: In an individual aged 65 years or older with normal or mild albuminuria, eGFR values consistently between 45 and 60 may be associated with a small increase in the 5-year risk of kidney failure compared with an eGFR of 60 to 89, but risks are so small (0.12%, especially compared with the risk of death) that any difference is irrelevant. The journey that patients complete over time is materially the same and very short.  

In clinical practice absolute risks are often more informative and useful to patients when making treatment decisions than relative comparisons. Although this is clinical epidemiology 101, most evidence we refer to in our clinical practice rely on measures of relative risk as opposed to absolute risk.

C360: What knowledge gaps remain on the impact of age in the diagnosis and management of CKD?

PL and PR: We do not know if eGFR is more variable in elderly individuals who may be more sensitive to changes in eGFR because of hydration status, reduced sense of thirst, and water intake.

 

Reference:

  1. Liu P, Quinn RR, Lam NN, et al. Accounting for age in the definition of chronic kidney disease. JAMA Intern Med. 2021;181(10):1359-1366. doi:10.1001/jamainternmed.2021.4813