Evaluating Long-Term Outcomes Across eGFR Equations in Older Adults.

Area of Science:

• Nephrology
• Geriatrics
• Epidemiology

Background:

• Current chronic kidney disease (CKD) diagnostic thresholds (eGFR < 60 ml/min/1.73 m²), based on the CKD-Epidemiology collaboration (CKD-EPI) creatinine equation, may lead to overdiagnosis in older adults.
• There is no established consensus on the optimal estimated glomerular filtration rate (eGFR) equation for older populations, leading to significant calculation variability.

Purpose of the Study:

• To investigate the impact of using eGFR equations validated for older adults (Berlin Initiative Study 1 [BIS1] and European Kidney Function Consortium [EKFC]) compared to the CKD-EPI₂₀₂₁ equation.
• To assess the implications of an age-adapted CKD definition (eGFR < 45 ml/min/1.73 m²) on CKD prevalence and health outcomes in older adults.

Main Methods:

• A cohort study utilizing data from the aspirin in reducing events in the elderly (ASPREE) trial and its observational follow-up (ASPREE-eXtension).
• Survival analyses compared risks of reduced disability-free survival (DFS) and major adverse cardiovascular events (MACE) between participants reclassified to different CKD stages using BIS1/EKFC versus CKD-EPI₂₀₂₁.
• Associations between eGFR and health outcomes were analyzed using restricted cubic splines.

Main Results:

• BIS1 and EKFC yielded eGFR values 12–15 ml/min/1.73 m² lower than CKD-EPI₂₀₂₁, increasing CKD prevalence from 21% to 37%–46%.
• Most participants were reclassified to a higher CKD stage, but long-term outcomes were similar between reclassified and nonreclassified groups.
• Risks of reduced DFS, all-cause mortality, or MACE were primarily observed below eGFR 45 ml/min/1.73 m², irrespective of urine albumin-to-creatinine ratio (uACR).

Conclusions:

• Employing older-age validated eGFR equations substantially increases CKD prevalence but does not identify additional high-risk individuals.
• Current CKD diagnostic thresholds may be inappropriate for older adults, especially when using equations validated for this demographic.
• Reconsidering CKD definitions within the context of aging is necessary to improve diagnostic accuracy and risk stratification.