title: Reproducibility of the ambulatory arterial stiffness index in hypertensive patients.
abstract: BACKGROUND
  We studied the repeatability of the ambulatory arterial stiffness index (AASI), which can be computed from 24-h blood pressure (BP) recordings as unity minus the regression slope of diastolic on systolic BP.
  
  
  METHODS
  One hundred and fifty-two hypertensive outpatients recruited in Nijmegen (mean age = 46.2 years; 76.3% with systolic and diastolic hypertension) and 145 patients enrolled in the Systolic Hypertension in Europe (Syst-Eur) trial (71.0 years) underwent 24-h BP monitoring at a median interval of 8 and 31 days, respectively. We used the repeatability coefficient, which is twice the SD of the within-participant differences between repeat recordings, and expressed it as a percentage of four times the SD of the mean of the paired measurements.
  
  
  RESULTS
  Mean AASI (crude or derived by time-weighted or robust regression) and 24-h pulse pressure (PP) were similar on repeat recordings in both cohorts. In Nijmegen patients, repeatability coefficients of AASI and PP were approximately 50%. In Syst-Eur trial patients, repeatability coefficient was approximately 60% for AASI and approximately 40% for PP. For comparison, repeatability coefficients for 24-h systolic and diastolic BP were approximately 30%. Differences in AASI between paired recordings were correlated with differences in the goodness of fit (r2) of the AASI regression line as well as with differences in the night-to-day BP ratio. However, in sensitivity analyses stratified for type of hypertension, r2, or dipping status, repeatability coefficients for AASI did not widely depart from 50 to 60% range.
  
  
  CONCLUSIONS
  Estimates of mean AASI were not different between repeat recordings, and repeatability coefficients were within the 50-60% range.
authors.affiliation: Department of General Internal Medicine, University Medical Centre St Radboud, Radboud University, Nijmegen, The Netherlands.
authors.forename: Dirk G
authors.initials: DG
authors.lastname: Dechering
authors.forename: Marijke S
authors.initials: MS
authors.lastname: van der Steen
authors.forename: Ahmet
authors.initials: A
authors.lastname: Adiyaman
authors.forename: Lutgarde
authors.initials: L
authors.lastname: Thijs
authors.forename: Jaap
authors.initials: J
authors.lastname: Deinum
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Eamon
authors.initials: E
authors.lastname: Dolan
authors.forename: Reinier Pm
authors.initials: RP
authors.lastname: Akkermans
authors.forename: Tom
authors.initials: T
authors.lastname: Richart
authors.forename: Tine W
authors.initials: TW
authors.lastname: Hansen
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kikuya
authors.forename: Jiguang
authors.initials: J
authors.lastname: Wang
authors.forename: Eoin
authors.initials: E
authors.lastname: O'brien
authors.forename: Theo
authors.initials: T
authors.lastname: Thien
authors.forename: Jan A
authors.initials: JA
authors.lastname: Staessen
mesh_terms: D000328:Adult; D000368:Aged; D001158:Arteries / Q000503:physiopathology*; D001794:Blood Pressure; D018660:Blood Pressure Monitoring, Ambulatory; D005260:Female; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests