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AASK Cohort Study
March 25, 2004
AASK COHORT PROTOCOL
TABLE OF CONTENTS
MARCH 25, 2004
Section Number Section 1. Summary
Pages in Section 1 are dated August 1, 2002 Section 2. Objectives and Research Questions
Pages in Section 2 are dated July 18, 2002 Section 3. Background and Rationale
Management of Hypertension
Environmental and Socio-Economic Factors
Relationship of Change in Proteinuria to Incident ESRD
Cardiovascular Disease (CVD) in the Setting of ESRD
Diseases Causing ESRD
Factors Associated with Renal Disease
Summary of Rationale and Significance
Pages in Section 3 are dated March 25, 2004 Section 4. African American Study of Kidney Disease and Hypertension (AASK) Trial.. 12 Background
Inclusion Criteria for the AASK Randomized Trial
Exclusion Criteria for the AASK Randomized Trial
Core Design of the Trial
Table 1. Overview of AASK Trial Design with Enrollment (n) by Randomized Group
Table 2. Characteristics of All Randomized Participants at Baseline and Characteristics of Active Participants (as of 9/14/2001) at Baseline And at Most Recent Visit
Trial Outcome Variables
Conduct of the Trial
Analysis Plan of the Trial
Summary of AASK Interim Results
Summary of AASK Main Results
Implication of AASK Trial Results for Cohort Study
Pages in Section 4 are dated August 1, 2002 March 25, 2004 i Section 5. Design of the AASK Cohort
Table 3. Key Dates Relevant to the Design of the AASK Study and the AASK Cohort Study
Contact Pattern and Data Collection Elements
Table 4. Data Collection Items and Activities by Visit During the First 2 Years of the AASK Cohort Study for Participants who have not Reached ESRD.
. 27 Table 5. Table of Data Collection Items and Activities by Visit for Participants Who reach ESRD after Enrolling in the Cohort Study
Table 6. Drug Titration Protocol in the AASK Study and Recommended Approach in the AASK Cohort Study
Patients Assigned to Beta-Blocker
Patients Assigned to Ramipril
Ambulatory BP Monitoring
Method of Renal Replacement Therapy (RRT)
Pages in Section 5 are dated March 25, 2004 Section 6. Analysis Section
Basic Renal Analytic Approach
Analyses of GFR Slope
Analyses of Predicted GFR Slope
Analyses of Clinical Renal Events
March 25, 2004 ii Analyses of Predicated GFR Slope
Analysis Plans for Specific Research Questions Listed in Section 2
Research Question 1
Research Question 2
Comparisons of Change in GFR to Change in Serum Creatinine
Research Question 3
Research Question 4
Research Question 5
Research Question 6
Research Question 7
Research Question 8
Projected Follow-Up and Power
Methods of Projecting Numbers of Future Events
Table 7. Minimum Detectable Increases in Relative Risk of Primary and Key Secondary Events for AASK and After-AASK Time-to-Event Analyses Based on ESRD, Serum Creatinine, and Death
Quality Assurance and Quality Control
Pages in Section 6 are dated October 1, 2002 Section 7. Organization and Administration
The 21 AASK Clinical Centers from the AASK Trial
The AASK Coordinating Center at the Cleveland Clinic
The National Institutes of Health
A Central Laboratory at the Cleveland Clinic
A Genetics Core Laboratory
A Cardiovascular Procedures Core Laboratory
Principal Investigators, Co-Investigators
Committees and Subcommittees
External Advisory Committee (EAC)
Measurements/Quality Control Subcommittee
Blood Pressure Management Subcommittee
Cardiovascular Outcomes Endpoint Subcommittee
Publications/Ancillary Studies Subcommittee
Study Coordinator/Retention Subcommittee
Protocol Changes and Amendments
Pages in Section 7 are dated August 1, 2002 Section 8. References
Pages in Section 8 are dated July 18, 2002
Despite excellent blood pressure control and despite use of reno-protective antihypertensive medication, hypertension-related renal disease commonly progresses. The factors that determine the progression of this condition remain poorly understood. The primary objective of the AASK Cohort Study is to determine prospectively the long-term course of kidney function and risk factors for kidney disease progression in African-Americans with hypertension-related kidney disease that receive recommended antihypertensive therapy. A secondary objective is to determine the occurrence of cardiovascular disease and assess its risk factors in the setting of hypertension-related kidney disease.
The AASK Cohort Study is a prospective, observational study that is an extension of the AASK clinical trial. The AASK trial was a randomized, clinical trial that tested the effects of 3 different medications used as first line antihypertensive therapy (ramipril, metoprolol and amlodipine) and 2 levels of blood pressure control (usual control and more aggressive control). Of the 1,094 randomized participants in AASK, it is anticipated that 650-750 individuals who have not reached ESRD will enroll in the Cohort Study. In addition, those individuals who reached ESRD during the AASK trial will be invited to attend one visit for collection of DNA. For those who enroll in the Cohort Study, twice each year, approximately every 6 months, exposures will be collected. Exposures will include environmental, genetic, physiologic, and socio-economic factors. The primary renal outcome will be a clinical outcome defined by doubling of serum creatinine, ESRD or death. Appropriate antihypertensive treatment (medications and target BP level as determined in the AASK trial) will be provided to all participants who do not have ESRD. In this fashion, the cohort will directly control two of the major ‘known’ determinants of kidney disease progression (treatment of hypertension and use of reno-protective, antihypertensive medication) and will therefore address its research objectives in the setting of recommended antihypertensive care. We anticipate a minimum of 4 contacts and maximum of 6 contacts for BP control per participant per year. The anticipated duration of follow-up in the Cohort Study will be 5 years (total of 9-12 years, including the period of the AASK trial).
It is anticipated that the AASK Cohort Study will provide data that enhance our understanding of the processes that determine progression of renal disease. Furthermore, data from this study might ultimately lead to new prevention strategies that delay or prevent the onset of ESRD.
August 1, 2002 1 Section 2. OBJECTIVES AND RESEARCH QUESTIONS The primary objective of the AASK Cohort Study is to determine prospectively the long-term course of kidney function and risk factors for kidney disease progression in African-Americans with hypertension-related kidney disease that receive recommended antihypertensive therapy. A secondary objective is to determine the occurrence of cardiovascular disease and assess its risk factors in the setting of hypertension-related kidney disease.
Research questions that will be addressed are as follows:
1. What is the long-term course of kidney function in this population?
2. What are the environmental, genetic, physiologic, and socio-economic factors which predict the progression of kidney disease?
3. What are the long-term effects of the AASK trial interventions on the progression of kidney disease?
4. Does the development of proteinuria predict the progression of kidney disease?
5. What is the impact of recommended blood pressure therapy, as determined by the AASK trial, on the progression of kidney disease in comparison to usual care in the community?
(Note: this question might be addressed using a corresponding subgroup of the CRIC cohort.)
6. What comorbidities, particularly cardiovascular disease, occur in the setting of hypertension-related kidney disease?
7. What risk factors predict the occurrence of cardiovascular disease?
8. What are the patterns of change in metabolic variables and cardiovascular-renal risk factors during the transition from pre-ESRD to ESRD?
July 18, 2002 2 Section 3. BACKGROUND AND RATIONALE During the past three decades, there has been a progressive decline in mortality from cardiovascular and cerebrovascular disease. In contrast, no such reduction in the mortality from end-stage renal disease (ESRD) has been observed and, in fact, in the past decade (1989-1998) the number of patients entering the ESRD program in the United States has doubled.
Consequently, there are now more than 300,000 patients receiving renal replacement therapy in the US at an annual cost to the Medicare ESRD Program of ~ $12 billion or about $43,000/patient/year (USRDS 2000). It has been well established that the leading causes of ESRD are diabetes mellitus and primary hypertension, accounting for nearly 70 percent of all ESRD in the United States (diabetes 43%; primary hypertension 24%) (USRDS 2000).
Demographic data suggest that those most susceptible to ESRD are the elderly ( 65 years) whose ranks have increased more than seven-fold in the last 2 decades, those of lower socioeconomic status, and minority groups, especially African Americans, who like the elderly, are disproportionately represented in the ESRD population when compared to their numbers in the general population (38.2% vs.13%).
Recent data from the USRDS (USRDS 2000) support older studies (Rostand, 1982) and show incidence rates of ESRD in African Americans that are about 4.5 fold greater than corresponding rates in white Americans of European ancestry. While this increased risk is found for nearly all forms of renal disease, the most important increased risks are from primary hypertension and diabetes mellitus because they affect the largest number of patients with ESRD. When compared to whites, African Americans have a nearly 5 fold greater incidence of ESRD due to diabetes mellitus, largely due to type II diabetes, and a 7 fold greater incidence of ESRD associated with primary hypertension, with the greatest difference seen in those under age 65 years. As a result, primary hypertension represents 34 percent of all ESRD in African Americans and when present in African Americans accounted for 9 percent of all ESRD in the US between 1995-1998 (USRDS 2000). In addition, data from the MRFIT and MDRD studies suggest a significantly greater rate of loss of renal function in African Americans with hypertension than in whites (Walker, 1992; Klahr, 1994; Hebert, 1997). Taken together these data suggest a unique susceptibility of African Americans to renal disease, especially from primary hypertension.
March 25, 2004 3 The relationship between blood pressure and kidney disease is graded,
continuous and progressive, such that the risk of ESRD increases throughout the range of blood pressure. Perhaps the most convincing evidence comes from the MRFIT study that recorded blood pressure in 332,544 men who were then followed for occurrence of ESRD over 16 years of follow-up (Klag, 1996). Relative to the category of optimal BP (SBP 120 and DBP 80 mmHg), the adjusted relative risk of developing all-cause ESRD was 1.2 for normal, 1.9 for high normal, 3.1 for Stage 1 hypertension, 6.0 for Stage 2 hypertension, 11.2 for Stage 3 hypertension, and 22.1 for Stage 4 hypertension. However, because of the high prevalence of Stage 1 and 2 hypertension, over 50% of ESRD cases occurred among persons with Stage 1 or 2 hypertension and 10% among persons with Stage 4 hypertension. In subsequent analyses from MRFIT, a similar pattern was present in African-American and white men; however, at any given blood pressure level, the risk of all-cause ESRD and hypertension-related ESRD was greater in African-Americans than whites (Klag, 1997). The differential between African-Americans and whites persisted after adjustment for blood pressure, cholesterol, income, diabetes and prior myocardial infarction.
One explanation for the susceptibility of African Americans to renal damage from hypertension may be that they have a greater duration or body burden of hypertension. African American children have higher blood pressure than their white counterparts (Gutgesell, 1981), and elevated blood pressure in childhood is associated with adult hypertension (VanLente, 1994). In addition, there is a high prevalence of non-dipping hypertension in African Americans (Gretler, 1994).
Since an impaired nocturnal fall in blood pressure may be a risk factor for renal deterioration (Timio, 1995), impaired circadian blood pressure rhythms together with a long duration of high blood pressure may contribute to progressive damage. Another factor that may increase the body burden of blood pressure is inadequate hypertensive therapy due to either no treatment (e.g., from limited access to health care or failure to seek medical attention) or inadequate treatment (e.g., from less intensive or effective therapies).