2011 USRDS Annual Data Report
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Introduction

Introduction to Volume One » CKD

Sections this chapter: 

This is the twenty-third annual report of the United States Renal Data System, and the twelfth in our atlas series. For the fourth 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, and the economics of the ESRD program.

The ADR has been shortened this year due to budgetary limitations, and the CKD and ESRD volumes have been bound together into one book. Chapters in the CKD volume have been limited to three or four spreads, and previous chapters on cognitive function, the transition to ESRD, and acute kidney injury have been omitted.

Chapters Top

This year's ADR presents data on the breadth of kidney disease and its impact on both individuals and society as a whole. To explore this idea, we turn this year to one of the most human characteristics of all — the ability to express ourselves through music. In the wide diversity of musical expression

We see similarities to the far-ranging impact of kidney disease across different racial and ethnic populations; in the lyrics of American music of the twentieth century — ranging from the Big Band era to folk music of the 1960s — we see expressions of emotion that can illustrate how kidney disease touches patients and their loved ones. The emotional implications of life with kidney disease, particularly for those on dialysis, are substantial, and relate not only to the physical elements of the disease but to its enormous financial stresses and its impact on personal relationships. Understanding these broad implications, we hope that the emotional connections expressed through American music help frame our reporting on kidney disease in the United States. 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). Improving on the MDRD method, a new estimating formula — the CKD-EPI equation — was published in the Annals of Internal Medicine in May, 2009; we compare these two equations, providing a perspective for readers on the strengths and weaknesses of each.

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 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 public health concern. In Chapter One we then define the CKD population, using NHANES data to examine how chronic conditions such as diabetes and congestive heart failure interact with CKD in a random sample of the U.S. population. We compare CKD populations identified through the MDRD and CKD-EPI equations, and address the burden of CKD across age, gender, and racial groups, as well as among patients with other chronic diseases. We also examine awareness, treatment, and control of hypertension, diabetes, and lipid disorders, and conclude with mortality prediction models, using both the MDRD and CKD-EPI equations.

Using data from the Medicare claims system and the employer group health plan datasets, we consolidate data on identification and care of CKD patients into Chapter Two. We begin by summarizing 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. We then illustrate the actual CKD burden in the NHANES population, and show that data gleaned only from the 585 diagnosis codes under-reports this burden. Data on laboratory testing of at-risk patients show that rates of evaluation for kidney disease — through urine microalbumin and serum creatinine testing — are low. 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 begin with comparisons of hospitalization rates in CKD and non-CKD patients, looking both at all-cause hospitalizations and at those for cardiovascular disease and infection, and giving particular attention to hospitalizations for infection. We conclude 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 and interventions, medication use, survival, and hospitalization. Data on prescription drug therapy are obtained from the Medicare Part D database, and address recommended therapies for major cardiovascular diagnoses and for patients receiving certain revascularization procedures.

This year we have added a chapter on Medicare Part D prescription drug use to both the CKD and ESRD volumes, defining the populations using the benefit and looking at various types of coverage, including the low income subsidy (LIS). We begin by looking at enrollment patterns in the general Medicare and CKD populations, then present data on monthly premiums, deductibles, gap coverage, and copayments. Data on the costs of Part D enrollment show total expenditures and per person per year (PPPY) costs; we also look at costs of specific medications in the general Medicare population and among those with early- or late-stage CKD. And, because CKD patients use substantial amounts of prescription drugs, we also look at their likelihood of reaching the coverage gap compared to that of their counterparts in the general Medicare population.

We conclude the CKD volume with Chapter Six, addressing the costs associated with CKD. We look at PPPY costs in the CKD population as a whole and in those with diabetes or cardiovascular disease, examine components of costs for CKD patients, and detail Medicare Part D costs by CKD stage, race, and LIS status.

Data Top

Data presented in this volume illustrate the challenges that CKD, its complications, and its costs pose to the healthcare system, to policy makers, and to the individuals and families facing this condition. Programs to detect CKD — some of which have been 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 highrisk population.

Beginning in 2010 (with codes for services implemented in July, 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 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 Researcher's Guide, USRDS database, and administrative oversight of the usrds are described in the introduction to Volume Two.

Maps in the ADR present data divided into quintiles. In the sample map on this page, 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; 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.