By Joseph E. Scherger, MD, MPH
Core Faculty, Eisenhower Health Family Medicine, Residency Program, Eisenhower Health Center, La Quinta, CA; Clinical Professor, Keck School of Medicine, University of Southern California, Los Angeles
SYNOPSIS: Older patients experience a physiological decline in estimated glomerular filtration rate. However, if the same levels are used to define chronic kidney disease for all adults, older patients not at a higher risk for kidney failure might still be classified with the disease.
SOURCE: Liu P, Quinn RR, Lam NN, et al. Accounting for age in the definition of chronic kidney disease. JAMA Intern Med 2021;181:1359-1366.
Investigators in Canada studied linked laboratory and administrative data that had accumulated from April 1, 2009, to March 31, 2017, for adults age 65 years and older with incident chronic kidney disease (CKD). Here, the authors defined CKD as an ongoing reduction in estimated glomerular filtration rate (eGFR) for more than three months below a fixed eGFR threshold or an age-adapted eGFR threshold. Non-CKD controls were age 65 years or older with a continuous eGFR of 60 mL/min/1.73 m2 to 89 mL/min/1.73 m2 for longer than three months and mild/normal albuminuria.
Compared to the age-adapted group, the fixed-threshold group was at a lower risk of kidney failure (1.7% vs. 3% at five years) and death (21.9% vs. 25.4%). In the fixed-threshold group, 75% of patients were age 65 years or older, with a baseline eGFR of 45 mL/min/1.73 m2 to 59 mL/min/1.73 m2 and mild/normal albuminuria. Compared to those in the non-CKD control group, the five-year risks of kidney failure and death among these older patients were similar. The risk of kidney failure was 0.12% or lower in both cohorts. The authors concluded current criteria for diagnosing adults with CKD may result in the overdiagnosis in seniors who are not at higher risk for kidney failure.
Controversy over the criteria for diagnosing CKD has been present in the nephrology literature over the past decade.1-4 Some academic nephrologists have called for age-related criteria for diagnosing CKD to avoid overdiagnosis in seniors. There are normal age-related changes in kidney function that do not increase the risk of kidney failure.5 Diagnosing any patient with a disease harms their sense of well-being, regardless of whether the disease is present.6
The eGFR measurement is a relatively new part of the routine chemistry panel. Serum creatinine remains a useful and reliable measure of kidney function. Some have called for an increase in the normal range for creatinine up to 1.5 mg/dL in seniors, especially those older than age 80 years.6 Since most of my patients are older than age 80 years, I reassure them daily their kidneys are fine and will live and function as long as they do. In primary care, we could reduce the referrals to nephrologists and avoid the CKD diagnosis in many seniors. The eGFR rate and serum creatinine level are important measures for the appropriate dosing of some mediations, and that is good geriatric practice.
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- Glassock R, Delanaye P, El Nahas M. An age-calibrated classification of chronic kidney disease. JAMA 2015:314:559-560.
- Levey AS, Inker LA, Coresh J. “Should the definition of CKD be changed to include age-adapted GFR criteria?”: Con, the evaluation and management of CKD, not the definition, should be age-adapted. Kidney Int 2020;97:37-40.
- Glassock RJ, Delanaye P, Rule AD. Should the definition of CKD be changed to include age-adapted criteria? YES. Kidney Int 2020;97:34-37.
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- Glassock RJ, Rule AD. Aging and the kidneys: Anatomy, physiology and consequences for defining chronic kidney disease. Nephron 2016;134:25-29.