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...criteria, common collection elements vital signs, biological samples, medication counts, and behavior changes. In trials where participants serve as their own controls and changes are analyzed over time, attendance at protocol visits is critical for achieving study goals.
To understand the success of the African American Study of Kidney Disease and Hypertension (AASK) in protocol adherence and subject retention, the authors examined why some participants came for their protocol visits and why others had barriers to the visit schedule. While recognizing that multiple factors can influence adherence, the authors chose a narrow definition of nonadherence--missing 3 consecutive visits (6 months) at least once during the trial.
The objective of the part of the study reported herein was to examine randomized treatment assignment and selected participant baseline characteristics that might predispose or place participants at high risk for nonadherence. The authors also identified strategies used by clinical centers to improve adherence and retention, particularly in those participants for whom this was an issue. Using the 3 ethical principles set forth in the Belmont Report (1976)--autonomy, beneficence, and justice--the authors demonstrated that excellent retention and adherence can be achieved.
Overview of AASK
AASK is considered a landmark trial and is the first study with over 1,000 African Americans with hypertensive renal disease. This is of particular importance because African Americans as a group (12% of the U.S. population) bear a disproportionately high burden of kidney disease and kidney failure due to hypertension (32% of the end stage renal disease [ESRD] population) (United States Renal Data System [USRDS], 2007). Most previous clinical trials have included all racial and ethnic groups. Some smaller studies have focused exclusively on African Americans and the medical issues affecting this population (Kusek, Agodoa et al., 1996). Despite some concerns that African Americans might be reluctant to participate in clinical trials, in the AASK Pilot study, 80% of the participants (N = 94) indicated a willingness to participate in further research studies (Kusek, Lee et al., 1996). The AASK researchers came from a variety of racial and ethnic backgrounds and included a large number of African Americans (planning committee members, investigators, study coordinators, and research staff).
AASK was a 7-year, 21-center, randomized, parallel group, multi-factorial, double blind trial sponsored by the National Institutes of Health/National Institute of Diabetes and Digestive and Kidney Diseases (NIH/NIDDK). The purpose of the study was to determine if one of two levels of blood pressure control and/or one of three classes of antihypertensive medication was more effective at slowing the rate of renal disease in African Americans with renal insufficiency presumed secondary to hypertension. Each participant was randomly assigned to either "usual" (mean arterial pressure [MAP] of 102-107 mmHg) or "low" (MAP of 92 mmHg or lower) blood pressure control plus primary treatment with one of three blinded antihypertensive regimens: calcium channel blocker (amlodipine [Norvasc[R]]), beta blocker (metoprolol succinate [Toprol XL[R]]), or angiotensin converting enzyme inhibitor (ramipril [Altace[R]]). The amlodipine arm was discontinued on 9/22/00 at the recommendation of the data safety monitoring board (DSMB). An interim analysis showed a slower decline in glomerular filtration rate (GFR) and progression to the study endpoints (rapid decline in kidney function, ESRD, and death) in both the metoprolol and ramipril groups as compared to the amlodipine group. The metoprolol and ramipril groups continued until the investigational portion of the trial ended on 9/30/01. Although the calcium channel blocker group was ended early, all participants in this group were followed by each clinical center per protocol until the end of the study. Therefore, all data until the conclusion of the trial were included in this paper.
Subjects were recruited and followed at 21 clinical centers with large African American populations. These were located across the United States with representation from the South (9), East (4), North Central (4), and West (4). Subjects were seen in outpatient hypertension/nephrology clinics or in General Clinical Research Centers (GCRCs) based in hospital or university settings. At many sites, the GFR visits, which ranged from 4-6 hours, were held at separate locations.
Educational background and training were similar in that all study coordinators had degrees in nursing, public health, medicine, or research. Support staff had backgrounds as medical assistants or some form of technical certification. All study staff were trained and certified at the beginning of the study and annually thereafter in all AASK procedures: implementation of protocol; data entry; GFR testing; blood pressure measurements using random-zero blood pressure monitors, and the collection, processing, and shipping of biological specimens.
Eligible participants were self-identified African Americans, ages 18-70 years who signed the consent form and had hypertensive renal insufficiency defined as [sup.125]I-iothalamate GFR between 20-65 ml/min/ 1.73 [m.sup.2]. Enrollment occurred over a 43-month period (February 1995-September 1998) and resulted in 1,094 participants. Following IRB guidelines for each site, clinical centers screened over 100,000 charts at clinics and medical practices looking for eligible serum creatinines, estimated renal function, and no other evident cause of renal disease. Individuals with diabetes were excluded from the study. A total of 2,802 potential participants were identified and, with permission from their primary care providers, were invited to have further screening. An ineligible GFR was the primary reason the remaining 1,708 participants did not meet entry criteria. In order to achieve assigned blood pressure goals, participants were prescribed, per protocol and at the discretion of the investigators, additional antihypertensive medications including diuretics. Participants were analyzed in both their assigned blood pressure group and their assigned medication group. Participants left the trial when they started dialysis, were transplanted, or died. They served as their own controls and were monitored, using [sup.125]I-iothalamate GFR, semiannually for changes in renal function. Protocol visits were conducted at 2-month intervals or more frequently if needed to achieve assigned blood pressure goal or to make medication adjustments. For some participants, this required intense weekly or biweekly follow-up. As is usual in clinical trials, some participants left the trial early for reasons other than defined end points. Reasons for premature withdrawal included...
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