RENAL RESEARCH INSTITUTE SYMPOSIUM The Longitudinal Chronic Kidney Disease Study: A Prospective Cohort Study of Predialysis Renal Failure Rachel L. Perlman,* Margaret Kiser,† Fredric Finkelstein,‡ George Eisele,§ Erik Roys,– Lei Liu,– Sally Burrows-Hudson,# Friedrich Port,** Joseph M. Messana,* George Bailie,§ Sanjay Rajagopalan,†† and Rajiv Saran** *Division of Nephrology, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, †Division of Nephrology, Department of Internal Medicine, University of North Carolina–Chapel Hill, Chapel Hill, North Carolina, ‡Yale Medical Group, Yale University, New Haven, Connecticut, §Division of Nephrology, Department of Internal Medicine, Albany Medical College, Albany, New York, –Department of Biostatistics, Kidney Epidemiology and Cost Center, School of Public Health, University of Michigan, Ann Arbor, Michigan, #Amgen, Inc., Thousand Oaks, California, **University Renal Research and Education Association, Ann Arbor, Michigan, and ††Department of Cardiovascular Medicine, University of Michigan, Ann Arbor, Michigan ABSTRACT Chronic kidney disease (CKD) is a significant public health problem:everyyearthenumberofAmericanslivingwithCKD andrequiringrenalreplacementtherapyincreases.Inaddition, individuals with CKD have substantially increased morbidity and mortality compared to the general population. The Longitudinal Chronic Kidney Dialysis (LCKD) Study is a multicenter, prospective, observational study of patients with moderate to severe CKD that was designed to better describe the course of the disease and the determinants of patient outcomes. Patients with moderate to severe CKD (glomerular filtration rate [GFR] < 60 ml/min/m 2 ) from four academic nephrology clinics were enrolled between 2000 and 2002. Specialcardiacandvasculartestinghasrecentlycommencedas phase II of this study. Areas that have been or are currently being studied include anemia management, health-related quality of life (HRQOL), medication use, and markers of cardiovasculardisease.ThisarticledescribestheLCKDStudy inthecontextofcurrentknowledgeofCKD. The incidence and prevalence of both chronic kidney disease (CKD) and end-stage renal disease (ESRD) continue to increase; kidney disease is a burden to patients and their families and is costly to the health care system. In addition, patients with CKD have a mortality rate significantly higher than the general population (1). Data from the National Health and Nutrition Examination Survey estimate that more than 7 million Americans have a glomerular filtration rate (GFR) less than 60 ml/min/1.73 m 2 and 700,000 individuals have a GFR < 30 ml/min/1.73 m 2 (2). In 2001 more than 96,000 patients developed ESRD; the incidence rate (per million) of ESRD has been steadily increasing over the last two decades and by about 5% per year over the past 5 years (1). Diabetes remains the most common etiology of renal failure, accounting for nearly 45% of patients who start dialysis. Hypertension is the second most frequent cause of ESRD, followed by glomerulonephritis and cystic kidney disease (1). There is significant evidence that better control of blood pressure, especially with the use of angiotensin- converting enzyme (ACE) inhibitors, can delay the need for dialysis, both among diabetic and nondiabetic CKD patients (3–5). There is also support for the notion that optimal pre-ESRD care can lead to health- ier patients starting dialysis in a more elective fashion, with fewer hospital days and lower morbidity (6). The Renal Research Institute (RRI) sponsored the LongitudinalChronicKidneyDisease(LCKD)Studyin the year 2000. The chief purpose of this study was to prospectively follow a cohort of patients with CKD in order to better understand the course of disease and determinants of patient outcomes. This article describes the LCKD study in the context of current knowledge about CKD, highlights several important areas being studied with data available from this cohort, and des- cribesnewdatathatarecurrentlybeingcollected,parti- cularly cardiovascular disease-related parameters and potentialbiomarkersofdiseasethatmeritfurtherstudy. Background Patients on dialysis represent only a small subset of patients with impaired renal function; many more Address correspondence to: Rajiv Saran, MD, MS, Division of Nephrology, University of Michigan, Kidney Epidemiology and Cost Center, 315 W. Huron, Suite 240, Ann Arbor, MI 48103-4262, or e-mail: rsaran@umich.edu. Seminars in Dialysis—Vol 16, No 6 (November–December) 2003 pp. 418–423 418