The conundrum of chronic kidney disease classification and end-stage renal risk prediction in the elderly--what is the right approach?

The worldwide high prevalence of chronic kidney disease (CKD) and the increasing number of patients reaching end-stage renal disease (ESRD) are a matter of major concern. The most widely accepted classification system of CKD is that proposed by the Kidney Disease Outcomes Quality Initiative (KDOQI) in 2002. When applying this system, it has become apparent that the prevalence of CKD is particularly high in elderly subjects. The fact that this system is mainly based on estimated glomerular filtration rate (eGFR), subdividing the severity of CKD into five stages, is a matter of debate. A main issue is that although a reduced eGFR is often encountered in elderly subjects, most of these subjects do not have a renal disease leading to an increased risk of ESRD, i.e. the predictive power of ESRD is unsatisfactory. Recent advances have been put forward to improve (1) estimation of GFR and (2) prediction of ESRD. In this review, we discuss the currently available data with a focus on the elderly and propose an improved classification system of CKD which is characterized by a substantially better diagnostic accuracy for progression to ESRD. This is simply and cost-effectively accomplished by subdividing stage 3 CKD into two groups (eGFR 30-44 and 45-59 ml/min/1.73 m(2)) and by complementing all levels of eGFR with information about urinary albumin excretion, i.e. whether normoalbuminuria, microalbuminuria, or macroalbuminuria is present. The consequence should be a revision of the 2002 KDOQI CKD classification system according to these findings, which would be a significant step forward, particularly for elderly CKD patients.