title: Design of the Dialysis Access Consortium (DAC) Aggrenox Prevention Of Access Stenosis Trial.
abstract: 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.
authors.affiliation: Nephrology Division, Veterans Affairs Medical Center and University of Iowa School of Medicine, Iowa City 52242-1081, USA. bradley-dixon@uiowa.edu
authors.forename: Bradley S
authors.initials: BS
authors.lastname: Dixon
authors.forename: Gerald J
authors.initials: GJ
authors.lastname: Beck
authors.forename: Laura M
authors.initials: LM
authors.lastname: Dember
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Depner
authors.forename: Jennifer J
authors.initials: JJ
authors.lastname: Gassman
authors.forename: Tom
authors.initials: T
authors.lastname: Greene
authors.forename: Jonathan
authors.initials: J
authors.lastname: Himmelfarb
authors.forename: Lawrence G
authors.initials: LG
authors.lastname: Hunsicker
authors.forename: James S
authors.initials: JS
authors.lastname: Kaufman
authors.forename: Jeffrey H
authors.initials: JH
authors.lastname: Lawson
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Meyers
authors.forename: John P
authors.initials: JP
authors.lastname: Middleton
authors.forename: Milena
authors.initials: M
authors.lastname: Radeva
authors.forename: Steve J
authors.initials: SJ
authors.lastname: Schwab
authors.forename: James F
authors.initials: JF
authors.lastname: Whiting
authors.forename: Harold I
authors.initials: HI
authors.lastname: Feldman
mesh_terms: D000465:Algorithms; D001166:Arteriovenous Shunt, Surgical; D001241:Aspirin / Q000494:pharmacology / Q000627:therapeutic use; D000068342:Aspirin, Dipyridamole Drug Combination; D003692:Delayed-Action Preparations / Q000627:therapeutic use; D004176:Dipyridamole / Q000494:pharmacology / Q000627:therapeutic use; D004338:Drug Combinations; D006083:Graft Occlusion, Vascular / Q000517:prevention & control*; D006801:Humans; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D016032:Randomized Controlled Trials as Topic; D006435:Renal Dialysis; D012107:Research Design; D018401:Sample Size; D014654:Vascular Patency / Q000187:drug effects
chemical_list: D000068342:Aspirin, Dipyridamole Drug Combination; D003692:Delayed-Action Preparations; D004338:Drug Combinations; D010975:Platelet Aggregation Inhibitors; D004176:Dipyridamole; D001241:Aspirin