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.
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.
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.
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.
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aDepartment of Pharmacology, University of Split School of Medicine, Split
bDepartment of Research in Biomedicine and Health, University of Split School of Medicine
cDepartment of Public Health, University of Split School of Medicine
dCroatian Centre for Global Health, University of Split School of Medicine, Split, Croatia
eCentre for Population Health Sciences, University of Edinburgh, UK
*Grgo Gunjaca and Ana Jeroncic contributed equally to the writing of this article.
Correspondence to Mladen Boban, Department of Pharmacology, University of Split School of Medicine, Soltanska 2, 21000 Split, Croatia.Tel: +385 21 557 904; fax: + 385 21 465 073; e-mail: email@example.com
Abbreviations: AIx, augmentation index; ASIs, arterial stiffness indices; BP, blood pressure; cAIx, central augmentation index; cPP, central pulse pressure; cSBP, central SBP; GTFs, general transfer functions; MAP, mean arterial pressure; MARS, multivariate adaptive regression splines; pAIx, peripheral augmentation index; pPP, peripheral pulse pressure; PWA, pulse wave analysis; PWV, pulse wave velocity
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Received 30 June, 2011
Revised 13 February, 2012
Accepted 3 April, 2012