of information into digestible learnings. These two invaluable components of the SIXTH EDITION distill numerous guidelines and consensus-based recommendations by level of evidence and grade of quality to improve our practices. ES! is the feeling that I had upon completing the SIXTH EDITION. You, the reader should review it, digest it, practice it, and also, enjoy it. I certainly did and still do. KAMYAR KALANTAR-ZADEH, MD, MPH, PHD UNIVERSITY OF CALIFORNIA, LOS ANGELES N E Y 4 CHRONIC KIDNEY DISEASE STAGING AND PROGRESSION by Gregory D. Krol Introduction Optimal management of patients with chronic kidney disease (CKD) requires appropriate interpretation and use of the markers and stages of CKD, early disease recognition, and collaboration between primary care physicians and nephrologists. Because multiple terms have been applied to chronic kidney disease (CKD), eg, chronic renal insufficiency, chronic renal disease, and chronic renal failure, the National Kidney Foundation Kidney Disease Outcomes Quality Initiative™ (NKF KDOQI™) has defined the all-encompassing term, CKD. Using kidney rather than renal improves understanding by patients, families, healthcare workers, and the lay public. This term includes the continuum of kidney dysfunction from mild kidney damage to kidney failure, and it also includes the term, end-stage renal disease (ESRD). Definition and Interpretation Management of CKD requires the clear understanding of its definition as proposed by the National Kidney Foundation (NKF). An informed interpretation of the estimated glomerular filtration rate (eGFR) is required, since the GFR is still considered the best overall index of kidney function in stable, non-hospitalized patients. Kidney damage is defined by any one of the following findings: a) pathologic kidney abnormalities b) persistent proteinuria c) other urine abnormalities, eg, renal hematuria d) imaging abnormalities e) eGFR 60 mL/min/1.73 m2 with no proteinuria because the overwhelming majority of such studies are normal. Epidemiology Persons with CKD have significantly higher rates of morbidity, mortality, hospitalizations, and healthcare utilization. The prevalence of CKD Stages 2–5 has continued to increase since 1988 as have the prevalences of diabetes and hypertension, which are respectively etiologic in approximately 40% and 25% of CKD cases. The current estimate is that 26 million US persons >20 y.o. have CKD. However, 15.2 % is the more recent CKD prevalence estimate, based on 2003–2006 NHANES data of U.S. adults aged 20 y.o., a decrease from the 15.9% cited in the NHANES data collected from 1999–2002. This decrease was reflected in CKD Stage 1 as Stage 3 increased to 6.5% from 2003–2006. The prevalence of CKD Stages 4 and 5 has doubled since 1988–1999, but has remained stable since 2002 at 0.6%. 6 CKD stage prevalence from NHANES 2003–2006 by the CKD-EPI equation are Stage 1, 4.1%; Stage 2, 3.2%; Stage 3, 6.5%; and Stages 4 and 5 combined, 0.6%. Stratified by age, all CKD stages were more prevalent in persons aged 60 y.o. (39.4%) than in those aged 40–59 y.o. (12.6%) or 20–39 y.o. (8.5%). By educational level, CKD at any stage was more prevalent among persons with less than a high school education (22.1%) than in persons with at least a high school education (15.7%). CKD prevalence was greater among non-Hispanic blacks (15.6%), nonHispanic whites (14.5%), and among other ethnicities (13.1%). The prevalences of diabetes and HTN in African Americans with CKD were 60.6% and 96%, respectively, compared to Caucasian prevalences of 45.7% and 90.7%, respectively (United States Renal Data Survey, 2010). Also, CKD prevalence was higher in diabetics than non-diabetics (40.2% v 15.4%), in those with cardiovascular disease (CVD) than in those without it (28.2% v 15.4%), and in those with HTN than in those without it (24.6% v 12.5%). For 2010, the estimated cost of ESRD is $28 billion, and projected as $54 billion by 2020. In the last quarter of 2009, the prevalence of ESRD (N=572,569, includes kidney-transplanted patients) was greater than in 2005 (N=485,012). In terms of incidence or newly-initiated ESRD patients, diabetes was etiologic in 37.5%, HTN 24.4%, glomerulonephritis 14.8%, cystic disease 4.7%, and others 18.6%. African American patients are 3.7 times more susceptible for development of ESRD, and Native Americans and Asians are 1.9- and 1.3 times more likely to develop ESRD. Recognition, Screening and Stratification of CKD Only 5% and 10% of the general Medicare population undergoes a screening urinalysis or a SCr, respectively. The NKF KEEP (Kidney Early Evaluation Program) screening program is a free community-based survey that identified individuals with CKD over the past 10 years. Since its inception, KEEP has screened >150,000 at-risk individuals with diabetes and/or HTN or those with a first-order relative with “known” kidney disease, diabetes, or HTN. Urine was evaluated for hematuria, pyuria and microalbuminuria. The KEEP population was better educated, had more insurance, and a higher prevalence of HTN, obesity, and diabetes than the NHANES cohort. Specifying CKD as “a low estimated GFR and/or presence of microalbuminuria,” 26% of KEEP/high risk participants had CKD nearly twice that noted in the general population