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CKD Volume1

Introduction to volume one » CKD

This is the twenty-fourth annual report of the United States Renal Data System, and the thirteenth in our atlas series.


For the fifth 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, 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, the economics of the ESRD program, and international comparisons. In Chapter Ten of Volume Two we also present new data on changes to patient care after the introduction of the bundled payment system in January, 2011.

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This year’s ADR presents data on the breadth of kidney disease and its impact on both individuals and society as a whole. Increased attention has been given recently to CKD, its progression to more advanced stages, and, most importantly, its high rates of adverse events, including death and end-stage renal disease. From a public health perspective, core issues center on prevention and on the preservation of kidney function over time.

To punctuate these issues, we turn this year to one of the most important preservation initiatives in the United States: the national parks. Yellowstone National Park, considered the first such park in the world, was established by an act signed by President Ulysses S. Grant on March 1, 1872; on August 25, 1916, President Woodrow Wilson signed an act creating the National Park Service. The parks, which preserve the national history of the United States’ most treasured sights and geographic locations, are visited by millions of Americans and foreign visitors each year, and often serves as spiritual places in which people may pause to consider how precious life is and the challenges faced in maintaining it.

In this ADR we reflect on the implications of kidney disease and on how this organ system can have such a widespread impact on health: on the functioning of the heart, brain, and nervous system, on hormonal balance, on bone and mineral metabolism, and on anemia and our ability to resist infections. The replacement of kidney function through a kidney transplant is certainly a new beginning, but it too has its challenges, not the least of which is preserving the function of the transplanted kidney over time.

The emotional implications of life with kidney disease are substantial, and relate not only to the physical elements of the disease but to the enormous stresses of financial issues and the impact on personal relationships. Understanding these broad implications, we hope that the emotional connections realized when viewing the breathtaking landscapes preserved in the national parks help give readers a broader perspective on the disease.

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 that indicate “true disease” in the kidney during the early stages of CKD, versus what is considered normal reduction in kidney filtering capacity. This is particularly challenging in the elderly. Improving on the method to define glomerular filtration, a new estimating formula — the CKD-EPI equation — was published in the Annals of Internal Medicine in May, 2009. In the past two ADRs we have compared the initial Modification of Diet in Renal Disease (MDRD) formula and the CKD-EPI equation, providing important insight into improvements in defining risk and disease burden. Since the CKD-EPI method has proven to have superior characteristics, we now use only this method in the ADR.

While the USRDS and others will continue to investigate these issues in both the clinical and public health arenas, already there are important data available on the impact of CKD, data based both on biochemical information and on the definition of the disease 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 must continue to evolve to help clinicians provide the best care to their patients affected by kidney disease.

In the Précis we highlight some of the most important data from the chapters, and address the burden of CKD — an area of major public policy and public health concern. In Chapter One we then define the CKD population, using NHANES data to examine how chronic conditions such as diabetes and cardiovascular disease interact with CKD in a random sample of the U.S. population. We show trends in risk groups, assess improvements in the awareness, treatment, and control of hypertension, diabetes, and lipid disorders, and conclude by looking at the impact of reduced kidney function on life expectancy.

Using data from the Medicare claims system and the employer group health plan datasets, we present data on identification and care of CKD patients in Chapter Two. We first summarize basic descriptive and comorbidity information from the major datasets used by the USRDS — the 5 percent Medicare sample, which includes individuals age 65 and older, and the MarketScan and Ingenix i3 databases, with employed populations that are 20 years younger. We then illustrate that while the identification of CKD is increasing in the health plan datasets, particularly for Stage 3, recognized disease in these datasets remains less than the actual burden shown in the NHANES estimates. Rates of testing for evidence of kidney disease, using serum creatinine and urine albumin tests in high-risk groups, are far lower than needed — a major concern.

We conclude the chapter by looking at the likelihood of receiving nephrologist care after a CKD diagnosis, and at prescription drug therapy among patients with CKD.

In Chapter Three we address morbidity and mortality among patients with CKD. We compare hospitalization and rehospitalization rates in CKD and non-CKD patients, giving particular attention to rehospitalization patterns related to the primary condition of the first event. Interestingly, CKD patients not only have higher overall hospitalization rates than those seen in the general population, but their rehospitalization rates are higher as well. These rates accelerate as patients progress toward ESRD, reflecting increasing complications which are challenging to manage on an outpatient basis. We conclude the chapter with data on mortality rates by CKD stage and across risk groups.

Cardiovascular disease in the CKD population is the focus of Chapter Four, in which we evaluate, by CKD stage, major cardiovascular diagnoses, types of evaluations, adverse events and interventions, and the broad area of medication use. Data on Part D prescription drug therapy address recommended therapies for major cardiovascular diagnoses and for patients receiving certain revascularization procedures.

This year’s chapter on Medicare Part D prescription drug use again defines the populations using the benefit, and looks at various types of coverage, including the low income subsidy (LIS). We begin by showing the top fifteen medications used by CKD patients, reflecting the totality of the disease burden faced by this population. We then look at enrollment patterns in the general Medicare, CKD, and ESRD populations with Part D coverage, and present data on monthly premiums, deductibles, gap coverage, and copayments.

Acute kidney injury is a condition with implications beyond the immediate event. In Chapter Six we bring back our examination of AKI, exploring trends in AKI hospitalization with and without the use of dialysis. We look at racial disparities, an area of major concern, at the medical conditions occurring with the AKI event, and at data on recurrent AKI events. We then focus on physician care after an event, at prescription drug therapy, and on changes in CKD stage.

Chapter Seven addresses the costs associated with CKD. We look at the relative burden of CKD versus other major chronic diseases such as diabetes and congestive heart failure, at per person per year costs, at costs by CKD stage and for Part D prescription drugs, and at the impact of the low income subsidy.


Data in this volume illustrate the challenges that CKD, its complications, and its costs pose to the healthcare system, policy makers, and individuals and families facing this condition. Programs to detect CKD — some ongoing since 2000 — have been initiated by the CDC and by non-profit patient organizations. 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 CKD patients is less than expected based on clinical practice guidelines; both issues may contribute to the increased morbidity and mortality of this high-risk population.

Begun in 2010, the CKD education benefit is intended to improve access to care, modality selection, consideration of home therapies, access to preemptive transplant, vascular access planning, management of risk factors, and referral to nephrologists and nutritional counseling for those with Stage 4 CKD. We plan to fully evaluate the implementation of the CKD education benefit in the 2013 ADR, when data are available for its first 18 months (codes for services were implemented in July, 2010).

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

Maps in the ADR present data divided into quintiles. In the sample map here, 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 the first and last boxes indicate the mean values of data points in the highest and lowest 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 does not usually match other data 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 in the calculation.