Defining renal risk.

Introduction The worldwide adoption of the Kidney Disease Outcomes Quality Initiative (K/DOQI) classification system for chronic kidney disease (CKD) [1] combined with the use of the Modification of Diet in Renal Disease (MDRD) study formula for estimating glomerular filtration rate (GFR) [2] has done much to raise awareness of the problem of previously undetected CKD. Recent observations indicate that as much as 16.8% of the US population may be affected [3]. This has led to many laudable efforts to increase screening for CKD and promote optimal treatment to slow CKD progression with the ultimate goal of reducing the requirement for renal replacement therapy. Nevertheless, these developments have also created new challenges. First, the optimal strategy for CKD screening has yet to be determined. It is clear that screening the entire population would not be cost effective [4]. It is therefore essential to develop a strategy that targets screening of patients at increased risk of developing CKD. Second, patients with CKD are a heterogeneous group and the risk of progression to endstage renal disease (ESRD) varies widely among patients with a similar GFR. Thus patients with CKD differ in their need for medical intervention as well as advice regarding the long-term prognosis associated with their diagnosis.