Chronic Kidney Disease in Cuba: Epidemiological Studies, Integral Medical Care, and Strategies for Prevention

Abstract

The experience of the Republic of Cuba regarding epidemiological studies, integral medical care, and strategies for the prevention of chronic kidney disease is summarized in this report. Cuba has a National Program for Chronic Renal Disease, Dialysis, and Renal Transplantation. There is a national nephrology net, integrated by the Institute of Nephrology as the coordinator center, that has 47 nephrology services with a hemodialysis unit (24 of them with peritoneal dialysis unit), 9 transplantation centers, 33 organ procurement hospitals, and 5 histocompatibility laboratories.

In 2004, the incidence rate in dialysis patients was 111 pmp, and the prevalence rate was 149 pmp, demonstrating an increasing mean of 17.0% and 10.0% per year, respectively. Renal transplantation rate was 16.6 pmp. The detection, registration, and follow-up of patients with chronic kidney disease (serum creatinine ≥1.5 mg/dL or glomerular filtration rate <60 mL/min) by family doctors was 9,761 patients, 0.87 patients per 1,000 inhabitants.

In the 1980s, three population-based screening studies were performed to define the burden of chronic renal failure in different regions of Cuba. The prevalence rate was 1.1, 3.3, and 3.5 per 1,000 inhabitants, respectively. At present, another three population-based screening studies are ongoing in order to detect the chronic kidney disease in earliest stages.

The continuing medical education activities have been very useful in raising the awareness of medical doctors and the basic health staff about the threats posed by and the strategies to prevent, diagnose, and treat chronic kidney disease.

Keywords:

• chronic kidney disease
• epidemiology
• prevention

INTRODUCTION

Chronic kidney disease (CKD), cardiovascular disease (CVD), diabetes, and hypertension associated with the elderly in the general population have a profound effect on morbidity, mortality, and health care expenditure. These diseases are leading to an epidemic burden worldwide, with the majority occurring in developing countries, and their tendencies are expected to continue growing for the next twenty years. This is why the International Society of Nephrology (ISN), the Latin-American Society of Nephrology and Hypertension (SLANH), and other regional scientific societies are asking for the implementation of strategies for their prevention.

The World Health Organization (WHO) recognizes that the chronic disease control is not necessarily expensive. Several clinics and public health interventions have the potential to reduce the burden of disease from CVD, diabetes, and hypertension significantly and at relatively low cost.[1] These diseases share risk factors and are closely related with the development and progression of CKD. In fact, the effective control of diabetes, hypertension, and CVD will lead to a beneficial effect for the prevention of CKD.

In 1970, a dialysis and renal transplantation program was initiated in Cuba that took into account the considerations mentioned previously. The Ministry of Public Health of Cuba launched the National Program for the Prevention of Chronic Renal Failure in 1996. This program shares preventive interventions with both the National Program of Non-Communicable Diseases and the National Program of Chronic Renal Disease, Dialysis, and Renal Transplantation.

The experience of Cuba in epidemiological studies for CKD, integral medical care of chronic renal patients in the primary health care, dialysis, renal transplantation, and strategies for prevention are described.

REPUBLIC OF CUBA

Demographic and Socioeconomic Data

Cuba is located at the entrance of the Gulf of Mexico in the Caribbean Sea. The total area is 110,922 km². The total population is 11,240,743 inhabitants, and the population density is 101 inhabitants per square kilometer.

Literacy rate is 96.2% and the mean educational level is ninth grade. The life expectancy in women is 78 years old and in men is 75 years old.

The growth of gross domestic product in relation to the previous year is 5.0%, and the gross domestic product per capita is 2,530.9 Cuban pesos (data from 2003). The health budget spending is 2,269,380,000 Cuban pesos and the health expenses per inhabitant is 201.99 Cuban pesos (data from 2004).[2]

National Health System

The national health system is unique, belong to the state with free access for the entire population. The country is divided in 444 health areas, each one with a policlinic for the ambulatory medical care and several family doctor offices in the community. There are 69,713 medical doctors; among them, 33,015 are family doctors. Family doctors and family nurses integrate the “basic health staff” in the community, covering the primary health care for the total population

Some basic indicators of the health care situation are (data from 2004):

• infant mortality rate: 5.8 per 1000 live births

• percent of surviving children at 5 years old: 99.2%

• index of low birth weight: 5.5%

• percent of infectious and parasitic diseases from the total number of death: 0.9%

• the main causes of death are mainly due to non-communicable diseases (e.g., heart disease, 186.9 deaths per 100 000 inhabitants; malignant neoplasm, 166.6; cerebrovascular disease, 73.6), as well as others. Diseases of arteries, arterioles, and capillaries, as well as diabetes mellitus are among the ten main causes of mortality.

Chronic kidney disease is related with all these diseases.[2]

COMMUNITY-BASED SCREENING AND HIGH-RISK POPULATION DETECTION FOR CHRONIC KIDNEY DISEASE

Background

In the 1980s, three epidemiological studies were performed to define the burden of chronic renal failure (CRF) in different regions of our country.

From 1984 to 1991, a screening and follow-up study was performed in known patients at high-risk for CKD registered by the family doctors in the province of Cienfuegos. The screening method used was the sulphosalicylic acid test for the detection of proteinuria; in cases that showed positive results for proteinuria, serum creatinine test was done and the glomerular filtration rate was estimated using the Cockcroft-Gault formula. The criterion for CRF was a GFR ≤70 mL/min. The prevalence rate was 1.1 per 1000 inhabitants.[3]

In 1988, two screening studies for CRF were performed at random samples of the general population. One of them in the province of Pinar del Río studied a sample of 9,580 persons. The screening method used was a “reactive strip of urea in spittle”[4]; in cases with positive results, serum creatinine test was done. The criterion for CRF was a serum creatinine >1.2 mg/dL. The prevalence rate was 3.5 per 1000 inhabitants.[5] Another study done in the province of Camagüey examined a population sample of 12,329 persons of one health area (policlinic). The screening method used was the serum creatinine; the criterion for CRF was a serum creatinine ≥141 µmol/L (1.59 mg/dL). The prevalence rate was 3.3 per 1000 inhabitants.[6]

Screening for CKD

The presence of chronic kidney disease in the earliest stages in the general community has just begun to be studied around the world. In Cuba, the prevalence of CKD in the earliest stages remains unknown. The epidemiological studies described previously were looking for patients with CKD in stages with CRF. At present, there are three ongoing epidemiological studies looking for the detection of the CKD in the earliest stages.

The objectives of these studies are as follows:

1. Define the frequency, distribution, pattern, and tendencies of CKD, CVD, diabetes, and hypertension.

2. Identify risk factors for the development and progression of these diseases.

3. Evaluate interventions aimed for prevention.

4. Implement a surveillance system.

The results of these studies may contribute to the implementation of prevention programs.

One of these studies is the project ISYS (Island of Youth Study). The Island of Youth is located 120 km in the south of Cuba. It has an area of 2,419 km² and a population of 86,614 inhabitants. In the first phase of the study, the main goal is to screen the total population for CKD, CVD, diabetes, and hypertension and the main risk factors shared by these diseases. The screening methods are a questionnaire, a urine test, and physical measurements for blood pressure, weight, and height. The urine test (Roche-Combur-10 Test) for density, ph, leukocytes, nitrates, proteins, glucose, ketones, urobilinogen, bilirubin, and blood was intended for all participants after informed consent was given. Persons who gave negative results of proteinuria and those who belonged to any of the high-risk groups defined by the project received a microalbuminuria test (Roche-Micral Test); serum creatinine test was done to determine those who showed positive results for proteinuria, microalbuminuria, or hematuria and who belong to any of the high-risk groups defined by the project. At present, 78,575 persons (90.72% of the total population) have completed the questionnaire, physical measurements, and urine test, and 11,510 persons have been studied with serum creatinine. The results of this study will be available at the beginning of the next year.

Two other epidemiological studies screening high-risk groups for CKD are also ongoing. One of them is in the province of Pinar del Rio, and the other one in the Cerro municipality in Havana City province. These three epidemiological studies have been conducted regarding the following conceptual model for screening.

Conceptual Model for Carrying out Step-by-Step the Screening for CKD, CVD, Diabetes, and Hypertension

Screening is the process by which unrecognized diseases or defects are identified by tests that can be applied rapidly on a large scale.[7] The screening test sorts out people without the disease or risk factors. It is not usually for diagnostic purposes, and it requires appropriate investigative follow-up for diagnostic confirmation and the treatment of new cases.

CKD met the criteria established by Wilson and Jüngner[8] for the practice of screening: the disease could prove to be serious if it is not diagnosed early, there was a high prevalence of preclinical stages and a long period between the first signs and the overt disease, and the natural history is not well understood yet.

The conceptual model for carrying out step-by-step the screening for CKD, CVD, diabetes, and hypertension in Cuba is shown in Figure 1.

Figure 1 Conceptual model for carrying out step-by-step the screening for chronic kidney disease, cardiovascular disease, diabetes, and hypertension.

In the first step, a simple questionnaire-based survey on major risk factors for CKD, CVD, diabetes, and hypertension; demographic data; and some physical measures of health risk should be administered. The inclusion of the following variables should be considered:

• risk factors for an increased susceptibility either to cardiovascular diseases or chronic kidney damage (examples: family history of CKD, CVD, diabetes mellitus, or hypertension; low birth weight; tobacco use; alcohol consumption; physical activity; and nutrition)

• risk factors that directly initiate chronic kidney damage (example: personal history of diabetes, hypertension, urinary tract infections, urinary stones, lower urinary tract obstruction, autoimmune diseases, systemic infections, drug toxicity, and hereditary diseases)

• physical measures (example: blood pressure, weight, height and body mass index).

It is desirable that all countries should be able to achieve this level of knowledge for the subsequent implementation of health promotion and preventive strategies for modifiable risk factors with a scientific base according to the specific conditions and resources of each country.

In the second step, a basic field survey should be administered that includes additional basic urine tests: proteinuria, hematuria, or microalbuminuria. Albuminuria or urine albumin/creatinine rate may be optional.

In the third step, a comprehensive field survey should be administered, adding an analysis of blood sample: serum creatinine and GFR estimated for any formula. Other blood analyses should be considered, such as glucose, total cholesterol, lipids, and GFR with endogenous creatinine.

In the fourth step, basic imaging tests should be administered, such as an ultrasound of the urinary tract. An electrocardiogram or echocardiography should be considered as well.

For making any decision regarding the second, third and fourth steps, the stratification of the population and high-risk groups as outcome of the first step should be taken into account.

INTEGRAL MEDICAL CARE AND STRATEGIES FOR PREVENTION

National Nephrology Net

The national nephrology net integrated by the Institute of Nephrology as the coordinator center for the National Program of Chronic Renal Disease, Dialysis, and Renal Transplantation has 47 nephrology services with hemodialysis unit, 24 of them with peritoneal dialysis unit. It also has 9 transplantation centers, 33 organ procurement hospitals, and 5 histocompatibility laboratories. There are 247 nephrologists and another 92 pediatricians and specialists in internal medicine dedicated to nephrology. There are 136 residents of nephrology.[9]

National Program for Chronic Renal Disease, Dialysis, and Renal Transplantation

The national program has four components: prevention in primary health care, clinical nephrology, dialysis, and renal transplantation. These components are integrated among them.

Prevention in Primary Health Care and Clinical Nephrology

The Ministry of Public Health of Cuba launched the National Program for the Prevention of Chronic Renal Failure in 1996, previously published in detail.[10] The implementation of preventive action has been in coordination with other programs of the national health system.

The reduction of risk has been reached in the following from 1996 to 2004: a significant reduction in low birth weight index, from 7.3% to 5.5%[2]; a reduction of incidents of smoking, from 36.8% to 33.2%; and better control of blood pressure (≤140/90 mmHg) in hypertensive patients, from 45.2% to 52.5% (Bonet M et al., I-II National survey of risk factors for chronic non-communicable disease, Cuba 1995–2000, unpublished data). A very low incidence (0.1%) of viral hepatitis B was seen in dialysis patients.[11] The vaccination against viral hepatitis B has been available in the dialysis units for many years, but since 2000, the vaccination had been extended for all CKD patients and diabetics registered by the family doctors in primary health care.

The detection, registration, and follow-up of patients of high-risk for CKD by family doctors has seen a significant growth from 1996 to 2004 (e.g., diabetics, from 201,137 [19.2 per 1000 inhabitants] to 342,371 [30.4 per 1000 inhabitants]; hypertensives, from 755,502 [72.0 per 1000 inhabitants] to 2,135,496 [203.7 per 1000 inhabitants], respectively).

The detection, registration, and follow-up of patients with CKD (serum creatinine ≥1.5 mg/dL or GFR<60 mL/min) by family doctors (see Figure 2) increased from 1996 (6,128; 0.59 per 1000 inhabitants) to 2002 (10,375; 0.92 per 1000 inhabitants) but decreased in 2003 and 2004 to 9,925 (0.88 per 1000 inhabitants) and 9,761 (0.87 per 1000 inhabitants), respectively.[12] The cause of this tendency may be related to a sub-registration of the patients.

Figure 2 Prevalence (per 1000 inhabitants) of known patients with chronic renal failure (CRF: serum creatinine ≥1.5 mg/dL). Registry of family doctors. Cuba 1995–2004.

Guideline for the Prevention, Diagnosis, and Treatment of CKD

In 2005, the “Guideline for the Prevention, Diagnosis, and Treatment of Chronic Renal Disease” by the Ministry of Public Health of Cuba was approved with the following objectives:

1. to improve the integral medical care and outcomes of the patients with CKD, CVD, diabetes, and hypertension;

2. to improve the knowledge and abilities of the medical doctors and basic health staff;

3. to reduce variability in medical care and contribute joining criteria in the scientific community.

The implementation of this guideline is ongoing in the national health system.[13]

Continuing Medical Education

Raising the awareness of medical doctors, the basic health staff, and patients about the threatening of CKD is ongoing. A course of “Prevention of Chronic Renal Failure” (40 hours) has been given to thousands of family doctors, nephrologists, pediatricians, nurses, and other members of the health staff, and a diploma in “Preventive Nephrology in the Community” (400 hours) targeting family doctors and the basic health staff has been given to hundreds of them. These continuing medical education activities are now being held across the country.

Dialysis and Renal Transplantation

Since the beginning of 1970, the development of renal replacement therapy (dialysis and renal transplantation) has made considerable progress.[9] Since 2002, a reorientation of the nephrology services was made to give an opportunity for dialysis patients to feel closer to the dialysis units and bring to the community a close relation with nephrologists. Also, it improves the interaction with the family doctors for the continuing joint management of the CKD patients in the policlinics (primary health care). Fourteen new nephrology services were created throughout the country. The dialysis acceptance rate (incidence) increased from 73 per million populations (pmp) in 2001 to 111 pmp in 2004. The prevalence rate increased from 115 pmp in the year 2001 to 149 pmp in 2004. The incidence rate increased a mean of 17.0% per year, and the prevalence rate increased a mean of 10.0% per year.

Renal transplantation is increasing from the beginning of the 1970s, reaching 205 renal transplantations (18.7 pmp) in 1994; the maxima were 248 renal transplantations (22.0 pmp) in 2002 and 185 (16.6 pmp) in 2004. However, the growth of renal transplantation cannot revert the growing prevalence of patients in dialysis over the last ten years.[9]

CONCLUSION

Cuba has a national program for the prevention and integral medical care of patients with CKD. The prevalence of CKD with glomerular filtration rate below 60 mL/min is known, as several epidemiological studies in the population has been conducted in this way; however, the incidence and prevalence of CKD in earliest stage remain unknown. Population-based screenings of CKD in earliest stage are being done in primary care settings. The incidence and prevalence of dialysis patients is increasing every year. Continuing medical education in regard to CKD has been very useful to raising awareness of medical doctors and the basic health staff in the primary health care about threats and strategies for the prevention, diagnosis, and treatment of CKD.

Strategies for facing this global health problem are required to improve public awareness, professional education, changes in the health policy, and the organization of the health services. Basic, clinical, and epidemiological researchers are also necessary in order to implement these strategies with a scientific base.

ACKNOWLEDGMENTS

The authors would like to acknowledge all the family doctors, nurses, nephrologists, and dialysis and renal transplant staff of Cuba for all of the data provided.