The fourth wave in chronic kidney disease (CKD) classification: Taking into account the aging kidney

Abstract

CKD afects more than 10% of the population worldwide, isstrongly associated with accelerated cardiovascular morbi-mortality, and its prevalence is exponentially higher amongolder individuals, although this prevalence is just based onestimated GFR (eGFR) and albuminuria [1]. The frst CKDclassifcation (2002) was proposed by the KDOQI group;it divided CKD into fve categories based on eGFR. Thisclassifcation was subsequently endorsed by the KDIGOorganization. The second CKD classifcation (2008) subdi-vided stage 3 into stages 3a and 3b (45–59 and 30–44 ml/min/1.73 m2, respectively), and incorporated the presenceor absence of albuminuria [2]. The third and currently usedKDIGO CKD classifcation (2012) added the albuminurialevel: normal (A1), moderate (A2), and severe (A3) [3]. Thepositive impact that implementation of the current classifca-tion has had is not debatable, however it does not take intoconsideration the age of the patient. Experts in nephrogeriat-rics have long suggested that eGFR declines as we age. Therate of decline has been suggested to be~1 ml/min per year,since 40 years of age, and the age-expected GFR (aeGFR)can be calculated using the equation developed by Kelleret al. [4, 5]; aeGFR (ml/min)=130 – age in years (±5).