title: A complex pattern of agreement between oscillometric and tonometric measurement of arterial stiffness in a population-based sample.
abstract: OBJECTIVE
  Arterial stiffness can be estimated by several noninvasive methods. In a large population-based sample we performed an agreement analysis of the set of arterial stiffness indices (ASIs) measured by tonometric (SphygmoCor) and oscillometric (Arteriograph) techniques.
  
  
  METHODS
  Central augmentation index (cAIx) and peripheral augmentation index (pAIx), as well as central SBP (cSBP) were measured in 1012 participants from a population-based study. Data were analyzed using Bland-Altman agreement analysis, multivariate adaptive regression splines and Fisher's linear discriminant analysis.
  
  
  RESULTS
  In contrast to high initial correlation between two devices (r = 0.87 for pAIx, 0.88 for cAIx and 0.95 for cSBP), plotting against each other the values of measured ASIs revealed their uneven distribution and grouping into three distinctive clusters of participants. The strongest cluster discriminators were age and DBP (cluster 1: age <40, DBP 70.42 ± 7.41; cluster 2: age >40, DBP 77.36 ± 10.16; cluster 3: age >60, DBP 82.56 ± 9.48). Bland-Altman analysis of clusters showed complex differences in agreement pattern for cAIx and pAIx. For cAIx SphygmoCor gives lower readings, especially in cluster 1, whereas for pAIx Arteriograph gives lower readings in cluster 1 and higher readings in clusters 2 and 3. The agreement for pAIx was better in younger participants and the same for cAIx in older participants.
  
  
  CONCLUSIONS
  ASIs obtained by SphygmoCor and Arteriograph cannot be interchangeably used as they seem to be differently influenced by predictors of arterial stiffness, predominantly by age. Different pattern of pAIx and cAIx agreement across clusters demonstrates importance of distinguishing cAIx and pAIx. Homogeneity of the study population for age should be considered when interpreting results of the studies investigating ASI.
authors.affiliation: Department of Pharmacology, University of Split School of Medicine, Split, Croatia.
authors.forename: Grgo
authors.initials: G
authors.lastname: Gunjaca
authors.forename: Ana
authors.initials: A
authors.lastname: Jeroncic
authors.forename: Danijela
authors.initials: D
authors.lastname: Budimir
authors.forename: Ivana
authors.initials: I
authors.lastname: Mudnic
authors.forename: Ivana
authors.initials: I
authors.lastname: Kolcic
authors.forename: Ozren
authors.initials: O
authors.lastname: Polasek
authors.forename: Igor
authors.initials: I
authors.lastname: Rudan
authors.forename: Mladen
authors.initials: M
authors.lastname: Boban
mesh_terms: D000328:Adult; D001158:Arteries / Q000503:physiopathology*; D001794:Blood Pressure; D003187:Compliance; D005260:Female; D006801:Humans; D008297:Male; D008365:Manometry / Q000379:methods*; D008875:Middle Aged