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Design of the Dialysis Access Consortium (DAC) Aggrenox prevention of access stenosis trial

Veterans Affairs Medical Center and University of Iowa School of Medicine, Iowa City, IA, USA; Nephrology Division, University of Iowa school of Medicine, E300D GH, 200 Hawkins Drive, Iowa City, IA 52242–1081, USA bradley-dixon{at}uiowa.edu

Gerald J Beck

Cleveland Clinic Foundation, Cleveland, OH, USA

Laura M Dember

Boston University School of Medicine, Boston, MA, USA

Thomas A Depner

University of California School of Medicine, Davis, Sacramento, CA, USA

Jennifer J Gassman

Tom Greene

Cleveland Clinic Foundation, Cleveland, OH, USA

Jonathan Himmelfar

Maine Medical Center, Portland, Maine, USA

Lawrence G Hunsicker

Veterans Affairs Medical Center and University of Iowa School of Medicine, Iowa City, IA, USA

James S Kaufman

Boston University School of Medicine, Boston, MA, USA

Jeffrey H Lawson

Duke University Medical Center, Durham, NC, USA

Catherine M Meyers

National Institute of Diabetes and Digestive and Kidney Disease, Bethesda, MD

John P Middleton

Duke University Medical Center, Durham, NC, USA

Milena Radeva

Cleveland Clinic Foundation, Cleveland, OH, USA

Steve J Schwab

Duke University Medical Center, Durham, NC, USA

James F Whiting

Maine Medical Center, Portland, Maine, USA

Harold I Feldman

University of Pennsylvania School of Medicine, Philadelphia, PA, USA

Background Surgically created arteriovenous (AV) grafts are the most common type of hemodialysis vascular access in the United States, but fail frequently due to the development of venous stenosis. The Dialysis Access Consortium (DAC) Aggrenox Prevention of Access Stenosis Trial tests the hypothesis that Aggrenox (containing dipyridamole and aspirin) can prevent stenosis and prolong survival of arteriovenous grafts.

Methods This is a multicenter, randomized, double-blind, placebo-controlled trial that will enroll 1056 subjects over four years with one-half year follow-up. Subjects undergoing placement of a new AV graft for hemodialysis are randomized to treatment with Aggrenox or placebo immediately following access surgery. The primary outcome is primary unassisted patency defined as the time from access placement until thrombosis or an access procedure carried out to maintain or restore patency. The major secondary outcome is cumulative access patency. Monthly access flow monitoring is incorporated in the study design to enhance detection of a hemodynamically significant access stenosis before it leads to thrombosis.

Results This paper describes the key issues in trial design, broadly including: 1) ethical issues surrounding the study of a clinical procedure that, although common, is no longer the clinical intervention of choice; 2) acceptable risk (bleeding) from the primary intervention; 3) inclusion of subjects already receiving a portion of the study intervention; 4) inclusion of subjects with incident rather than prevalent qualifying clinical conditions; 5) timing of the study intervention to balance safety and efficacy concerns; and 6) the selection of primary and secondary study endpoints.

Conclusions This is the first, large, multicenter trial evaluating a pharmacologic approach to prevent AV graft stenosis and failure, an important and costly problem in this patient population. Numerous design issues were addressed in implementing the trial and these will form a roadmap for future trials in this area.

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