Epidemiologic basis for the prevention of renal disease

A public health approach to preventing ESRD requires targeted stepwise primary, secondary and tertiary prevention programs to intervene at various stages in the natural history of renal disease. The NKFS collects, aggregates and reports data on renal disease in the Singapore population. These data are currently gathered through population-based and work-site screening programs conducted throughout the island. Information generated from this surveillance program is then processed to steer the secondary and tertiary intervention programs. In addition, data on risk factors for renal disease are used to define the prevalence of risk factors for chronic renal insufficiency in the country.

These data also have research applications. For example, the racial constitution of Singapore provides a unique opportunity to evaluate risk factors for renal disease among Chinese, Malays and Asian Indians. These are racial groups that represent the bulk of the Southeast Asian region, such that conclusions derived from the study of these three subpopulations in Singapore may be generalizable to other countries in the region. Such detailed epidemiologic study is timely given the existence of racial differences in the incidence of ESRD, with the Malay community characterized by a markedly higher rate as compared to their Chinese or Indian counterparts⁴.

Target populations

A consideration in the development of the NKFS prevention program was the importance of combining both a population-based and a high-risk prevention strategy. The high-risk strategies focus on the members of the population with particular risk factors for renal disease. While such an approach tends to be more cost-effective, the high-risk strategy does not remove the risk factors that lead to disease, as it tends to be largely palliative⁵. The population-based approach seeks to modify the determinants of disease in the population as a whole, and potentially have a larger impact on reducing the rates of disease⁶. This approach relies heavily on public education, but incorporates activities that remove obstacles to healthy behavior.

The epidemiology of ESRD in Singapore was also a significant factor influencing the prevention program. Approximately 50% of incident cases of ESRD are attributed to diabetes and hypertension⁴. Surveillance data on the level of blood pressure and glycemic control for patients with diabetes mellitus and hypertension demonstrated sub-optimal control⁷, leading the NKFS to initiate interventions that target such patients at high risk for developing renal complications and ESRD. The health care delivery system of Singapore is such that the bulk of chronic outpatient care is conducted by primary care practitioners who are paid at the point of contact⁸. An absence of a medical insurance scheme is associated with the lack of an opportunity to monitor clinical outcomes of the patients. Combined with the unaffordability of chronic outpatient for complex diseases like diabetes, hypertension and renal disease, Singapore faces outstanding impediments to the optimal management of such patients. Thus, programs that focus on preventing the onset of renal complications of diabetes and hypertension would need to be designed in order to address current obstacles and prepare for future hurdles to better patient care. In addition, these programs would need to be developed and implemented in close partnership with the primary care practitioner community of the country.

THE NKFS PREVENTION PROGRAM

The NKFS developed its prevention program around a framework of the natural history of disease development and progression Figure 1. Diseases, in particular the chronic "lifestyle" related diseases such as diabetes, hypertension and some forms of renal disease, occur because of a combination of genetic and environmental factors (point A in Figure 1). The onset of the majority of chronic illnesses is insidious and asymptomatic (point B). Disease is detected and diagnosed when symptoms develop (point C) or through screening interventions. Without proper treatment, or in certain cases despite adequate treatment, complications such as ESRD may develop. This eventually results in death (D). These stages of the disease process are points at which interventions can be tailored.

Figure 1.

A framework for a public health approach to prevention. Each boxed area corresponds to specific programs of the NKFS. Points A and B correspond to the Primary Prevention and Early Detection Programs, points C and D correspond to the Secondary Prevention and Intervention Programs.

Full figure and legend (25K)

The Primary Prevention and Early Disease Detection Program

The Primary Prevention and Early Disease Detection Program of the NKFS seeks to: (1) educate the general public regarding risk factors for renal disease and other chronic diseases; (2) identify individuals at risk for or who have early renal disease and associated chronic diseases; and (3) identify through epidemiologic studies the unique determinants of renal disease and disease progression in this multi-racial Southeast Asian population (points A and B in Figure 1). These three objectives are intimately intertwined in a series of population-based and high-risk public education and screening programs. If effective, screening for risk factors and for the early stages of renal disease and associated diseases, shifts the point of diagnosis and intervention from clinical or symptomatic disease closer to the disease onset or pre-clinical phase (point C to B in Figure 1). This "lead time" markedly improves the patient's outcome, since early intervention is associated with a significant advantage over late intervention in the treatment of early renal insufficiency, as well as for diabetes mellitus and hypertension^9,10. The program's population-based initiatives include a (1) workplace screening, (2) community-based screening, (3) school screening, and (4) public education campaign.

Health Screening Program

For the adult populations, after providing consent, each subject is asked to complete a self-administered questionnaire regarding demographic information, medical history and family history of renal disease, diabetes and hypertension. Screening is then done for proteinuria, hypertension, diabetes as well as their known risk factors such as hypercholesterolemia, body mass index, waist-hip-ratio, lifestyle characteristics and family history. The screening activities are performed at sites convenient to the participants such as worksites, community centers, mobile screening buses, and shopping malls.

Referral of individuals with abnormalities

Individuals identified to have risk factors or abnormalities on screening receive on-site counseling from trained staff nurses. These nurses had undergone a five-day training program that tested their ability to perform, interpret and counsel on clinical information derived from the various screening tools. Those detected to have abnormalities are asked to pursue further evaluation with their primary care physicians. Within a week of completion of screening, the designated screening nurse conducts a telephone call to determine whether the follow-up visit has been completed.

The pediatric program focuses on the 12-year school age population and seeks to identify children with urinary abnormalities and hypertension. Details of this program have been published elsewhere¹¹.

The program's high-risk initiatives include a longitudinal screening program of 5000 taxi drivers who undergo repeated screening for a ten-year period. This population is considered at somewhat increased risk for the development of renal disease and other chronic diseases based on their clinical and demographic characteristics. This program was initiated in the year 2000 and includes banking of blood and urine for study of future biochemical and genetic markers, as well as a validated local nutritional survey in order to identify dietary determinants of disease. A second program performs systematic screening of family members of NKF Singapore ESRD patients.

To date, over 450,000 Singaporeans have participated in the NKF screening initiatives. Preliminary analysis reveals that racial differences exist in the risk factors for proteinuria in this population (abstract; Ramirez et al, J Am Soc Nephrol 12:239A, 2001), that systolic and diastolic blood pressure levels not traditionally classified as elevated are associated with proteinuria (abstract; ibid), that proteinuria begins to occur at markedly lower body mass index levels among certain racial groups (abstract; Ramirez et al, J Am Soc Nephrol 12:240A, 2001), and that elevated random blood glucose levels identified by screening are associated with proteinuria in a non-diabetic population (abstract; Ramirez et al, J Am Soc Nephrol 12:155A, 2001). In addition, differences exist in the identified rates of urinary abnormalities in the various screening groups Table 1. As judged by their high-risk state, the taxi drivers and family members of the ESRD patients have a much higher prevalence of proteinuria at 5.8 and 8.1%, respectively. There also appears to be a relatively high baseline prevalence of hematuria in the various populations screened. Detailed analyses of these populations are currently being performed.

Table 1 - Prevalence of urinary abnormalities in screening populations.

Full table

Public education campaign

At each interaction with the public, education messages are disseminated. In addition, a comprehensive public communications program is one of the critical components of prevention. Prior to the conceptualization of this public communications strategy, analyses of the target audiences were completed. The communication media, the content and message delivered, as well as measurements of efficacy of the program were then tailored to each of these target audiences. Unique cultural difficulties in communicating the importance of prevention, early screening and intervention in renal disease care were taken into consideration. These include the fatalistic attitudes of certain segments of the public, variations in educational level, as well as the difficulty in promoting prevention as a relevant concern. As is well-recognized, prevention is a particularly challenging concept; there is a significant lag-time between intervention and outcome, and there is no perceived immediate difference between those who adopt healthy lifestyles and those who do not¹².

With these in mind, the NKF Singapore public education campaign for prevention comes in various formats that include public lectures, concerts, enlistment of popular entertainment celebrities as health ambassadors and ethnic-specific television drama programs. A specific communications program has been designed for the school-aged children, with access to over 80% of all of the nation's schools. Members of the public can obtain free health information at Kidney Resource Centers that are attached to NKF dialysis units. There is a prevention road show, which involves a bi-monthly discussion and presentation to community leaders about the importance of early detection, intervention and renal disease prevention. In addition, the NKFS organizes a highly successful annual charity show through its partnership with the leading television channel in the country. The charity show aims to educate the public about the NKF Singapore's prevention and dialysis programs. Finally, each encounter at an NKFS health screening site serves as an opportunity to educate the public on renal and chronic disease prevention on an individual basis. Indirect markers of the program's reach to the public is evidenced by the observation that two out of three Singaporeans donate regularly to the NKFS programs and that the charity show has a record-breaking viewership rating. Over time, the ability of these communication messages to alter health practices will need to be evaluated.

The secondary prevention and intervention program

Because of the high incidence of ESRD attributed to diabetes and hypertension in the country⁴, the poor glycemic and blood pressure control for patients with diabetes and hypertension⁷, the observation that the majority of patients with diseases that lead to ESRD have access to varied levels of comprehensive care (including an inter-disciplinary clinical care team), the secondary prevention and intervention program focuses on patients with known diabetes mellitus and hypertension (points C and D in Figure 1). The goal of this component of the NKFS prevention program is to intervene in the natural progression of diabetes, hypertension and renal disease through the elevation of the standards of comprehensive treatment of diabetes and hypertension and the prevention of their associated complications. Although the primary focus of this component is the improvement of care of patients with diabetes and hypertension in order to prevent the onset and progression of renal complications, it is believed that this strategy could serve as a framework to facilitate the care of a patient with any medical condition, including early chronic renal insufficiency of other etiologies.

This program, which is in the phase of implementation, will have two inter-related components: (1) the provision of a systematic approach for the management of patients with diabetes mellitus and hypertension to the general practitioner community; (2) the development of a network of NKFS Prevention Centers that will provide supportive inter-disciplinary clinical care services to the patients of the medical community.

Disease management program

The NKFS, in collaboration with a diabetes disease management provider, is in the process of implementing a diabetes disease management system¹³ that has been shown to significantly improve both short- and long-term clinical outcomes in various populations, including the American Indian Community [abstract; Rith-Najarian et al, Diabetes 48(Suppl 1): A193, 1999]. Disease management programs, which provide a multi-disciplinary systematic, evidence-based approach to clinical care, have been demonstrated to result in significant clinical and economic impact for complex chronic diseases¹⁴. In order to increase the likelihood that the medical community will participate in the program, 10% of the total general practitioner population of the country participated in an NKFS-facilitated process of evaluation and modification of the existing clinical care algorithms to take into account the health care resources and unique health care needs of the Singapore patient population. Supplementing the development of the disease management system is a continuing medical education program. The first phase of this program, which focused on the adaptation of the clinical care algorithms was recently completed and full-scale implementation will occur in the first quarter of 2002.

Team-based chronic renal disease, hypertension and diabetes care

Complementing this program is the creation of a network of NKFS Prevention Centers, which aim to provide necessary team-based comprehensive clinical care services for patients who are managed by the medical community. These nurse-run clinics will provide long-term patient education, dietary management and specialized screening for early complications of diabetes and hypertension (microalbuminuria, retinal photography, podiatric care). The nurse educators will coordinate the care of these patients from their primary care practitioner to specialty services, and will ensure patient compliance with prescribed therapy. Furthermore, the centers will serve as an opportunity to monitor patient care and measure clinical outcomes. The first of these NKFS Prevention Centers will open in the first quarter of 2002.

SUMMARY

At present, studies that definitively demonstrate the effectiveness of population-based screening for renal disease are not available. Randomized clinical trials would be the ideal methodology to evaluate the effectiveness of this comprehensive, population-based approach to disease prevention. However, such trials are not generally feasible because of the requirement of large sample sizes of communities and the long period of observation. As an alternative, statistical simulations of screening programs may provide indirect evidence of the cost-effectiveness of such programs.

Despite the lack of such data, the NKFS has proceeded to design and implement nationwide prevention and screening initiatives because of the burden of renal disease in the country. In response to the evolving health care issues in Singapore, it is in the process of active implementation of a program with the long-term goal of reducing the continued increase in ESRD in the country. This is being done through a public health approach that involves primary prevention, public education and screening, early intervention, provision of comprehensive clinical services, and the education of the primary care physician community. An equally important aspect is the clinical and epidemiologic research components of the prevention program, since these will provide clear benchmarks for improvement as well as determine future directions of the program. Furthermore, long-term monitoring of the benefits of the screening components of the NKFS prevention program may provide additional data as to the efficacy of such screening programs to reduce the burden of ESRD.

Finally, these lessons from NKFS will amplify those learned from prevention programs in the United States, such as the National Kidney Foundation's Kidney Early Evaluation Program (KEEP) and the National Kidney Disease Education Program of the NIDDK¹⁵. Recommendations and observations from these multiple initiatives can be utilized to develop effective communication and public education strategies that suit the unique population of the individual country seeking to develop similar prevention programs.

References

References

Acknowledgments

Partial funding for this program is from the Kwan Im Thong Hood Cho Buddhist Temple, Singapore.