2010 USRDS Annual Data Report
This Chapter
Download PDF
Download all slides
*corresponding data in Excel included
Search This Page
Search All

An introduction to chronic kidney disease in the united states   Top

Sections this intro:  

     This is the twenty second-annual report of the United States Renal Data System, and the eleventh in our Atlas series. For the third year we include a volume on chronic kidney disease (CKD), defining its burden in the general population, and looking at cardiovascular and other comorbidities, adverse events, preventive care, prescription medication therapy, care during the transition to ESRD, and costs to Medicare and employer group health plans. In Volume Two we provide information on the size and impact of the end-stage renal disease (ESRD) population — the traditional focus of the USRDS — presenting an overview of the ESRD program, along with detailed data on incidence, prevalence, comorbidity of new ESRD patients, severity of disease, clinical care, hospitalization and mortality rates, pediatric patients, renal transplantation, the provider delivery system, and the economics of the ESRD program.

      We approach Volume One from the perspective that the implications of CKD were under-appreciated prior to February, 2002, when a new CKD classification staging system was proposed. The five-stage system was developed using population-level data from the National Health and Nutrition Examination Survey (NHANES), a surveillance system coordinated by the National Center for Health Statistics at the Centers for Disease Control and Prevention. The conceptual model of this system was based on similar approaches for populations at risk for diabetes and hypertension, two well-known diseases that damage the kidney as well as other organ systems. The model characterizes progressive stages of CKD, from early evidence of kidney damage — such as albumin in the urine — to overt reductions in the filtering capacity of the kidney, defined by the estimated glomerular filtration rate (eGFR).

      There are many issues related to defining the levels of eGFR and urine albumin which indicate "true disease" in the kidney during the early stages of CKD, as compared to a normal reduction in kidney filtering capacity, particularly in the elderly. A new estimating equation was published in the Annals of Internal Medicine in May, 2009, improving on the MDRD method; we compare these two equations, providing a perspective for readers on the strengths and weaknesses of each. The USRDS and others will continue to investigate these issues in both the clinical and public health arenas, but already there is important data available on the impact of CKD, data based not only on biochemical information, but on the disease as defined within the Medicare and health plan datasets. The impact of the CKD staging system as a predictor of morbidity and mortality is now well known on a population level, but its translation into the care of individual patients is another matter.

Chapters  Top

      The 2008 ADR was the first to include a volume dedicated to CKD; this year we expand the volume to ten chapters, including an analysis of acute kidney injury as well as a chapter on cardiovascular disease. New this year is a chapter on the transition between CKD and ESRD in nursing home patients, and analyses of medication use under the Part D prescription drug benefit, which began in 2006.

      In the Prιcis we highlight some of the most important data from the chapters, and address the burden of CKD — an area of major public policy and health concern. In Chapter One we then define the CKD population, using NHANES cohorts over a 20-year period, and looking at the burden of chronic conditions such as diabetes and cardiovascular disease. We also compare CKD populations identified through the MDRD and CKD-EPI equations, and address the degree of biochemical and clinical abnormalities. We conclude with analyses of awareness, treatment, and control of cardiovascular risk factors, and an assessment of mortality rates by eGFR, race, and gender.

      Basic descriptive and comorbidity information from the major datasets used by the USRDS — the 5 percent Medicare sample, and the MarketScan and Ingenix i3 databases — is summarized in Chapter Two. We use laboratory data from the Ingenix i3 LabRx dataset to define, by CKD stage, levels of typical biochemical parameters. Remarkably, the abnormalities identified here are quite similar to those in the NHANES population-level data. We also demonstrate the consistency of the relationship between CKD defined from actual laboratory data and that reported by diagnosis codes on claims for services.

      In Chapter Three we address the care of patients with CKD, looking at the likelihood of urine microalbumin testing based on diabetic and hypertensive status. Testing rates are surprisingly low, particularly among patients with hypertension — known for its associated risk of kidney disease. We then report on the use of prescription medications, including ACEIs/ARBs, beta blockers, calcium channel blockers, lipid lowering agents, diuretics, ESAs, oral Vitamin D, and phosphate binders, and examine the degree of lipid and glycemic control.

      Hospitalization and mortality across chronic disease conditions are examined in Chapter Four, along with hospitalizations for pneumonia, bacteremia/sepsis, and urinary tract infections, and trends in adjusted rates of mortality. Although increased recognition of kidney disease can bias the patient cohort over time, adjustments for severity of disease help reduce this bias, and demonstrate that survival has improved.

      Cardiovascular disease in the CKD population is the focus of Chapter Five, in which we evaluate, by CKD stage, major cardiovascular diagnoses and interventions, medication use, survival, and hospitalization.

      Chapter Six addresses the transition to ESRD in the institutionalized elderly entering nursing homes, using data from the Medicare Minimum Data Set. We first compare general nursing home patients to those with CKD and ESRD, then examine how memory, decision making, and the ability to make oneself understood change over time after admission to a nursing home. We also look at physical function in the non-CKD, CKD, and ESRD populations, and conclude with analyses of survival.

      Chapter Seven addresses the transition from CKD to ESRD, a period of great concern, and one which may contribute to high mortality in the first months on dialysis. We illustrate the timeline for recognition of CKD prior to ESRD, and present data on visits to primary care physicians and to specialists among patients who reach ESRD, assessing when providers begin to recognize the trajectory of the disease in this vulnerable population.

      In Chapter Eight we continue our analysis of acute kidney injury (AKI) and its relationship to CKD and ESRD. Recognized AKI has been increasing in both the Medicare and the younger EGHP populations. We examine the type of dialysis used, if any, and the underlying diagnoses. We then look at follow-up after discharge, determining which physicians see these patients and what role nephrologists play in the first year after AKI. We have also added data on medication use and on rehospitalization for AKI.

      We conclude with Chapter Nine, addressing the costs associated with CKD, and introducing new analyses comparing costs in the U.S. and Taiwan. We also present data on prescription drug costs in 2007 under the new Part D benefit.

Data  Top

      Data presented in this volume illustrate the challenges that CKD, its complications, and its costs pose to the healthcare system and to policy makers. Programs to detect CKD have been initiated by the CDC, and the National Kidney Foundation's Kidney Early Evaluation Program (KEEP) has been ongoing since 2000. By their nature, detection programs are broad-based approaches to define, through the use of simple tests, populations at risk of a disease or its complications, targeting individuals for detailed evaluation and intervention. The data we present here indicate that the CKD population is under-recognized, and that care of both the CKD population as a whole and of those patients transitioning to ESRD is less than optimal; both issues may contribute to the increased morbidity and mortality of this high-risk population.

      The CKD education benefit for Medicare patients begins in 2011, with the intent to improve access to care, modality selection, consideration of home therapies, access to preemptive transplant, planned vascular access, management of risk factors, and referral to nephrologists and nutritional counseling. We plan to follow trends in these key aspects of care to determine the impact of this new benefit, and to examine how it might affect the high first-year mortality among hemodialysis patients.

      The USRDS website, Researcher's Guide, database, and administrative oversight are described in the introduction to Volume Two.

      Maps in the ADR present data divided into quintiles. In the sample map, for example, approximately one-fifth of all data points have a value of 10.8 or above. Ranges include the number at the lower end of the range, and exclude that at the upper end (i.e, the second range here is 8.2–< 9.2). To facilitate comparisons of maps for different periods, we commonly apply a single legend to each map in a series. In this case the data in each individual map are not evenly distributed, and a map for a single year may not contain all listed ranges. Numbers in gray indicate the mean values of data points in the highest and lowest quintiles; these can be used to calculate the percent variation between quintiles.

      The Excel page for each map (on our website and CD-ROM) includes additional data. The map-specific mean is calculated using only the population included in the map; this will usually not match data presented elsewhere in the ADR, and should be quoted with caution. The overall mean includes all patients for whom data are available, whether or not their residency is known. We also include the number of patients excluded in the map-specific mean, and the total number of patients used for the overall calculation.