Current CKD Definition Takes into Account Both Relative and Absolute Risk

Delanaye et al.1 propose that GFR thresholds to define CKD should depend on age. Specifically, people aged≥65 years with GFR 45–59 ml/min per 1.73 m2 and albumin-creatinine ratio<30 mg/g should not be classified as having CKD. This is not a new proposal. It has been discussed many times, including by the Kidney Disease Outcomes Quality Initiative in 2002 and Kidney Disease Improving Global Outcomes (KDIGO) work groups in 2009 and 2012.2 Each time, the consensus was that the GFR threshold for the definition of CKD should be age-independent. Delanaye et al. now reopen the discussion, suggesting that the GFR threshold for the CKD definition should be determined only by relative risks for mortality. They cite data from the CKD Prognosis Consortium, the largest meta-analysis, showing that the relative hazard of mortality for eGFR 45–59 versus 75–89 ml/min per 1.73 m2 with albumin-creatinine ratio<30 mg/g was lower at older age. However, they do not mention the higher absolute risk of mortality (two to four times higher at the oldest compared with youngest group).3 Absolute risk is more important than relative risk to patients and providers. The threshold for CKD should also take into account outcomes beyond mortality such as ESKD, AKI, heart failure, and hospitalization which are often more specific and sensitive consequences of CKD, and have substantial excess risk in older age. Many other diseases, such as hypertension and diabetes, follow a similar pattern of higher prevalence at older age with smaller relative risks but higher attributable risks of mortality and complications. Yet, the hypertension and diabetes guidelines define these diseases independently of age while recommending evaluation and management personalized to age and other factors. Similarly, the KDIGO guideline recommends an age-independent definition but personalized evaluation and management. The CKD definition has been stable since 2002, enabling great progress in the field. The age-independent GFR threshold has been widely accepted by nephrology societies across the world, endorsed by the World Health Organization, and incorporated into the International Classification of Disease Coding System. At each deliberation, the expanding evidence base has supported the original definition. We think that changing the GFR threshold at older age on the basis solely of relative risk of mortality while ignoring the higher absolute risk for mortality and other outcomes is a narrow view that impedes progress. We believe it is time, as a nephrology community, to move the discussion to optimizing management and discovering new therapies. DISCLOSURES None.

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