Chronic Kidney Disease Surveillance Research Articles

Epidemiology of CKD in Europe: an uncertain scenario

In the large, diachronic scenario of systemic epidemiology, chronic kidney disease (CKD) is a component of a new epidemic of diseases that, over the twentieth century, replaced malnutrition and infection as leading causes of mortality in the population [1]. Neoplasia, cardiovascular and respiratory diseases and diabetes are ascending the priority rank in the global-health agenda. These diseases reduce life expectancy and engender disability in all population strata including the poorest segment of the population, a stratum still considered to be mainly hit by infectious diseases. Public health interventions calibrated to the level of challenge that these diseases impose are now considered as a great opportunity of averting death and adverse clinical outcomes in developed as well as in developing countries. In 2005, the World Health Organization (WHO) emphasized that chronic diseases are a global priority [2]. It was calculated that, if governments are able to put in place public health policies that produce a 2% yearly reduction in mortality rates for chronic diseases, an achievable goal, 36 million deaths would be prevented worldwide between 2005 and 2015 [3]. The WHO department of Measurement and Health Information estimates that almost 80% of life-years that could be gained by such policies would come from deaths averted in people aged under 70 years [3], i.e. from the most active population strata. Even more than a health priority, the goal of reducing mortality rates by chronic diseases is an economic priority because it could save about 10% of the loss in income due to death and disability which amounts to $8 billion in the developing countries only [4]. Limitation of two major environmental risk factors, salt intake and smoking, and the use of cardiovascular drugs in high-risk patients are of proven cost effectiveness not only in high-income but also in lowand middle-income countries [5]. Appropriate health policies could be very effective, and measures adopted over the last three decades in Poland and Finland are an instructive demonstration of how much can be achieved with simple, well-targeted interventions. In the early 1990s, the Polish government reduced subsidies on animal fats. Polyunsaturated oils such as soya bean and rapeseed oil substituted saturated animal fat in the diet of Polish people, and as a consequence coronary heart disease mortality dropped by more than 25% between 1991 and 2002, a dramatic effect which could not be explained by increased fruit consumption or decreased smoking [6]. The educational campaigns and public policies adopted in Finland in the 1970s [7] represent a paradigmatic example of how much can be achieved in terms of population health by the adoption of a well-articulated intervention plan. In most western countries, the epidemic of cardiovascular disease, diabetes and neoplasia is receiving increasing attention by the public and policymakers. Yet, the CKD epidemic remains largely a ‘silent’ epidemic. The nephrology community is making a worldwide-extended, major effort for raising the status of CKD among chronic diseases, and the World Kidney Day has now become the icon of such a tantalizing effort [8]. Yet, the yields of these efforts have still to materialize. The face-to-face comparison with diabetes is a case in proof. Diabetes and CKD have a similar prevalence in the general population, and part of the clinical outcomes of diabetes are accounted for by CKD triggered by this disease. Promoting prevention programmes focussing on diabetes is legitimately considered as a major public health goal in most western countries, and this disease is, in various European countries, included among priority research themes for funding. In contrast, most health authorities literally ignore CKD prevention. The improving Kidney Outcome Global Initiative (KDIGO) poses surveillance of CKD by periodic surveys or by specific registries as a means for monitoring the epidemic at country level [9]. Prevention of end-stage renal disease (ESRD) was set as a specific goal of ‘Healthy people 2010’, a health-promotion and disease-prevention initiative which was started in the USA in 1979 [10]. However, until very recently, official documents released by the European Community or by the majority of European Community governments did not even mention CKD as an issue of public health concern. A 2007 report on health in Italy [11], one of the largest European countries, released by the national institute of statistic (ISTAT) did not even include CKD among chronic diseases, and similar ignorance of the problem is traceable in contemporary documents prepared by high-level agencies of other countries.

Epidemiology of Chronic Kidney Disease Among Normotensives

Among adults in the United States, 1 in 4 has hypertension and 1 in 8 has chronic kidney disease (CKD). Although the relationship between hypertension and CKD has been recognized for several hundred years, the prevalence of CKD among patients with normal blood pressure has not been assessed in randomly sampled populations. Crews et al1 in this issue of Hypertension are the first to report such estimates: 13.4% of people who have normal blood pressure have CKD. Among those with prehypertension, the prevalence is 17.3%; among those with undiagnosed hypertension, the prevalence is 22.0%; and among those with diagnosed hypertension, the prevalence is 27.4%. The magnitude of these CKD prevalence estimates is astounding and may even be misleading unless placed in appropriate context. The awareness of CKD diagnosis was dismal: <10% of people were aware of CKD regardless of hypertension category. A thorough analysis of the definition of CKD is necessary to understand how the varying definitions of CKD may have influenced both the prevalence and awareness estimates. The prevalence estimates may be inflated because of CKD that is so mild that it may not be considered a disease at all. For example, examination of the Figure (derived from Table 3 of the article) shows that if one considers the prevalence of more severe CKD defined as macroalbuminuria or estimated glomerular filtration rate (GFR) <45 mL/min per 1.73 m2, then the prevalence estimates fall dramatically. These stricter definitions of CKD yield the following prevalence estimates of CKD: normal blood pressure 0.5%; prehypertension 1.0%; undiagnosed hypertension 2.0%; and <5.0% prevalence of CKD among those with diagnosed hypertension. These prevalence estimates are much lower than those obtained with the more sensitive definition that is typically used to define CKD. Thus, the prevalence estimates of CKD may be driven up …

Establishing a National Chronic Kidney Disease Surveillance System for the United States

Despite the recognized importance of chronic kidney disease (CKD), the United States currently lacks a comprehensive, systematic surveillance program that captures and tracks all aspects of CKD in the population. As part of its CKD Initiative, the Centers for Disease Control and Prevention (CDC) funded two teams to jointly initiate the development of a CKD surveillance system. Here, we describe the process and methods used to establish this national CDC CKD Surveillance System. The major CKD components covered include burden (incidence and prevalence), risk factors, awareness, health consequences, processes and quality of care, and health system capacity issues. Goals include regular reporting of the data collected, plus development of a dynamic project web site and periodic issuance of a CKD fact sheet. We anticipate that this system will provide an important foundation for widespread efforts toward primary prevention, earlier detection, and implementation of optimal disease management strategies, with resultant increased awareness of CKD, decreased rates of CKD progression, lowered mortality, and reduced resource utilization. Final success will be measured by usage, impact, and endorsement.

The Kidney

Today, it is universally acknowledged that, in hypertension, the kidney is both culprit and victim.1 Kidney malfunction causes hypertension, and hypertension, in turn, aggravates chronic kidney disease (CKD) and accelerates its progression. High blood pressure (frank hypertension and blood pressure values in the high normal range) are clearly correlated to progressive kidney injury, both in experimental2 and in clinical3 observations. All of the current guidelines4,5 recommend lowering of systolic blood pressure to 130 or 125 mm Hg in CKD, and even lower values are recommended if the target level of proteinuria of <1 g per 24 hours has not been achieved.4 There is good evidence of “renoprotection” by lowering blood pressure in patients with renal disease, at least in the presence of proteinuria.3 In CKD patients without proteinuria, eg, autosomal polycystic kidney disease, further renoprotection cannot be achieved by lowering blood pressure below the target blood pressure recommended in patients without CKD6; nevertheless, these patients have a markedly elevated cardiovascular risk, and more stringent lowering of blood pressure is desirable, because, eg, reduction of left ventricular hypertrophy as an index of cardiovascular risk had been documented in such patients.6 The worldwide problem of neglect of hypertension and of insufficient implementation of antihypertensive treatment in CKD patients prompted the International Society of Nephrology and the International Federation of Kidney Foundations to devote this year’s World Kidney Day (http://www.worldkidneyday.org) on March 12th to the issue …

Public Health Surveillance of CKD: Principles, Steps, and Challenges

Population-based surveillance of disease has become an important component of addressing such common chronic diseases as hypertension and diabetes. Such systems guide screening, prevention, and treatment resources. Development of a chronic kidney disease (CKD) surveillance system for the United States that focuses on early stages of CKD is an important activity that could help stem the increasing number of end-stage renal disease cases and CKD-related morbidity and mortality in the United States. It also could help in the evaluation of interventional programs that currently are being developed or already in place. Such a surveillance system should address the burden of CKD, awareness of CKD, CKD risk factors, CKD consequences, process and quality of care in CKD, and the health system capacity for CKD. It also should allow for estimations of the burden of CKD by age, sex, race/ethnicity, socioeconomic strata, geographic groups, and clinical subgroups. We describe the key components of a surveillance system for CKD, steps in the development of such a system, and challenges that need to be addressed. Information necessary for surveillance of CKD is evolving. At this juncture, collecting, integrating, analyzing, and interpreting information about CKD for surveillance by using a systematic, comprehensive, and feasible approach will be instrumental in prevention and health promotion efforts for this chronic disease.

CKD Surveillance Using Laboratory Data From the Population-Based National Health and Nutrition Examination Survey (NHANES)

Surveillance for chronic kidney disease (CKD) using nationally representative samples of the US population is central in providing information about the magnitude and trends in CKD burden that will guide disease management and prevention planning for clinicians and public health authorities. We used a cross-sectional study design to estimate the change in prevalence of CKD over time by using National Health and Nutrition Examination Survey (NHANES) data. NHANES III (1988-1994) included 15,488 participants and NHANES rounds 1999-2004 included 13,233 participants older than 20 years with serum creatinine measurements who were examined in a mobile examination center. Early stages of CKD were defined by glomerular filtration rate (GFR) estimated by using the Modification of Diet in Renal Disease (MDRD) Study equation and urinary albumin-creatinine ratio following the classification system established by the National Kidney Foundation's Kidney Disease Outcomes Quality Initiative. Moderately decreased GFR increased in prevalence from 5.4% to 7.7% (P < 0.001) and severely decreased GFR increased from 0.21% to 0.35% (P = 0.02) from 1988-1994 to 1999-2004. Within CKD stage 3, 18.6% +/- 1.6% (SE) of individuals should be referred to a nephrologist following a proposed set of criteria for referral; referral rates were highest for individuals with diabetes and lower in whites compared with other race-ethnicity groups. These survey data suggest that the prevalence of CKD has increased between 1988-1994 and 1999-2004. Surveillance for early stages of CKD (stages 1 to 4) should monitor these and other trends.

CKD Surveillance Using Administrative Data: Impact on the Health Care System

The US Renal Data System Coordinating Center identifies patients with chronic kidney disease (CKD) in administrative data sets and determines the overall size of the population with a diagnosis of CKD, with such major comorbid conditions as diabetes and congestive heart failure, and associated expenditures. A 2-year observation period is used to define individuals with at least 1 International Classification of Diseases, Ninth Revision, Clinical Modification diagnosis code from inpatient claims or at least 2 from outpatient claims or physician and supplier service claims for kidney disease and comorbid conditions. This method is applied to the 5% general Medicare data and extrapolated to the general Medicare population. In the Medicare and dually enrolled Medicare/Medicaid populations, 8% to 10% have CKD or end-stage renal disease, and these groups account for 27% to 35% of expenditures. Hospitalization rates for all patients with cardiovascular disease, congestive heart failure, infection, and pneumonia are greatest for dialysis patients and patients with CKD compared with patients without CKD. Regarding detection in groups at high risk of CKD, approximately 1 in 5 patients with diabetes, only 1 in 50 patients with hypertension, and 1 in 4 patients with diabetes and hypertension had at least 1 microalbuminuria test in a year. CKD is a major pubic health issue with large financial implications. Continued surveillance and detection programs are needed to address the burden of disease, level of comorbidity, and access to care. Long-term trend analyses are needed to determine whether morbidity and mortality rates change based on greater detection and treatment efforts.

Individuals With a Family History of ESRD Are a High-Risk Population for CKD: Implications for Targeted Surveillance and Intervention Activities

Activities intended to improve the detection, treatment, and control of chronic kidney disease (CKD) should be incorporated into existing health care systems and targeted to high-risk populations to avoid redundancy and waste of resources. One high-risk population consists of first- or second-degree family members of patients with end-stage renal disease (ESRD), who are 2 to 3 times as likely to have incident ESRD, have high rates of impaired kidney function and undetected and uncontrolled high blood pressure, and are more likely to be obese. These individuals usually are unaware of their underlying CKD and may discount their own risk of ESRD. The ESRD Network 6 Family History Project shows that the ESRD Networks, which constitute a national CKD surveillance system for patients with stage 5 CKD, may be an existing resource that can be used to identify relatives of incident patients with ESRD and provide these families with information about CKD. Nationally available resources have been developed by the National Kidney Disease Education Program for use with these at-risk families. Individuals interested in population-based CKD control activities should be aware of and use these resources.

The Kidney Early Evaluation Program (KEEP): Program Design and Demographic Characteristics of the Population

Chronic kidney disease (CKD) recently was identified as a public health problem requiring a public health prevention approach. The National Kidney Foundation Kidney Early Evaluation Program (KEEP), initiated in 2000, meets the definition of a public health program, offering surveillance and early detection of CKD. This report aims to detail demographic characteristics of KEEP participants and compare them with characteristics of participants in the National Health and Nutrition Examination (NHANES) 1999-2004. KEEP is a CKD screening program enrolling individuals 18 years and older with a family history of kidney disease or personal or family history of diabetes or hypertension. Simple descriptive statistics were used in the analysis. For comparison, the NHANES sample was restricted to participants with hypertension or diabetes or a family history of hypertension or diabetes. The number of KEEP participants grew exponentially over time. Most participants were aged 46 to 60 years. KEEP enrolled twice as many women as men (68.4% versus 31.5%). Minorities were well represented (33.4% African American, 12.3% Hispanic). Almost 58% of participants had some college or more education, and close to 85.0% had a physician. Compared with NHANES, the KEEP population was older and included a larger proportion of women and African Americans. Self-reported hypertension, self-reported diabetes, obesity, and CKD were higher in KEEP (52.9% versus 38.5%, 26.6% versus 9.9%, 43.6% versus 35.5%, and 22.8% versus 17.6%, respectively). KEEP has been successful in enrolling individuals at risk of kidney disease, evidenced by the high levels of self-reported hypertension and diabetes.

High Prevalence of Chronic Kidney Disease among Patients with Sleep Related Breathing Disorder (SRBD)

Sleep apnea syndrome, a sleep-related breathing disorder (SRBD) of which obstructive sleep apnea syndrome (OSAS) is representative, is often associated with obesity, and therefore patients with SRBD might have a high prevalence of chronic kidney disease (CKD). However, the relationship between obesity and the prevalence of CKD has not yet been investigated in a large cohort of patients with SRBD. The Okinawa Nakamura Clinic Sleep Apnea Syndrome (ONSLEEP) registry contains records for all patients evaluated by full-scale polysomnography (PSG) from September 1990 to the end of 2003 (n=5,651). We studied the total of 4,056 (71.8%) of these patients who had an apnea hypopnea index (AHI) of more than 5 events per hour. The glomerular filtration rate (GFR) was estimated using the abbreviated Modification of Diet in Renal Disease equation in the 1,624 patients for whom serum creatinine data was obtained at the time of the PSG. We defined CKD as a GFR of less than 60 mL/min/1.73 m2. The mean age was 49.9+/-13.5 (mean+/-SD) years; the mean body mass index (BMI) was 28.4+/-5.0 (mean+/-SD) kg/m2. We compared the findings with those from participants in the 1993 general screening registry in Okinawa (n=94,267). From among the total 94,267 screening participants, we selected 7,454 subjects who were age- and sex-matched to the experimental group with SRBD; the ratio of cases to controls was thus approximately 1:4. CKD was detected in 496 (30.5%) patients, with SRBD a higher incidence than that in the screened population (9.1%); the adjusted odds ratio (95% confidence interval) was 4.542 (3.922-5.260, p<0.0001). In contrast to the screened population, the prevalence of CKD decreased as BMI increased (it was 35.7% in SRBD patients with a BMI<25.0 kg/m2, 31.4% in those with a BMI 25.0 to 29.9 kg/m2, and 25.2% in those with a BMI > or =30.0 kg/m2); in the controls the values were 8.1%, 10.5%, and 10.6%, respectively. Taken together, these results suggest that surveillance of CKD is warranted among SRBD patients, particularly those who are not obese.