CKD Classification

The number of patients with ESRD is increasing worldwide. Despite recent advances in our understanding of the uremic state and improvements in the science and technology of renal replacement therapy, the morbidity and mortality of these patients is unacceptably high: More than 20% per year. Moreover, the health care cost of treating ESRD exceeds $17 billion annually in the United States alone.1 These observations led the nephrology community a few years ago to recognize chronic kidney disease (CKD) as an important public health problem while emphasizing the need for timely treatment for prevention of ESRD. Among a large number of initiatives aimed at increasing early awareness of CKD, the National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) clinical practice guidelines for classification and staging of CKD receives most attention and acceptance.2 In addition to a working definition, KDOQI proposes a classification system based on severity determined by level of kidney function, calculated from the estimated GFR (eGFR), irrespective of the cause of kidney disease. The KDOQI CKD definition and classification are widely accepted in clinical practice and influential in epidemiologic studies worldwide. Nevertheless, the classification is the subject of increasing scrutiny by investigators,3 regulators, and even members of the original KDOQI workgroup.4 A controversial aspect of KDOQI is the high prevalence of CKD imposed by the classification system itself. Use of KDOQI leads to prevalence estimates of combined stages 1 and 2 CKD ranging from 2.9 to 7.0% in the general population.5 In other studies, stage 3 CKD prevalence …