Ambulatory arterial stiffness index: reproducibility of different definitions.

Background: Ambulatory arterial stiffness index (AASI) has been proposed as a marker of arterial stiffness, which predicts cardiovascular mortality. This study compared the reproducibility of 24-h, daytime, night time, and symmetrical AASI.

Methods: A total of 126 untreated hypertensives (mean age 48.2 +/- 10.7 (s.d.) years, 70 men) underwent 24-h ambulatory blood pressure (ABP) monitoring twice 2-4 weeks apart. The reproducibility of AASI was assessed using the following criteria: (i) repeatability coefficient (RC = 2 x s.d. of differences); (ii) RC expressed as a percentage of close to maximal variation (pMV = RC/(4 x s.d. of the mean of paired recordings)); (iii) coefficient of variation (CV); (iv) concordance correlation coefficient (CCC); (v) agreement (kappa) between the two AASI measurements to detect subjects at the top quartile of the respective AASI distributions.

Results: There was no difference in average AASI values between the two assessments. For 24-h, daytime, night time, and symmetrical AASI, respectively, (i) RC values were 0.24, 0.38, 0.42, and 0.30; (ii) pMV 49.6, 68.8, 73.9, and 56; (iii) CV 40.3, 39.3, 62.9, and 116.3; (iv) CCC 0.60, 0.35, 0.28, and 0.52; (v) agreement 82.5% (kappa 0.54), 72.2% (0.28), 73% (0.22), and 81.7% (0.50). Differences in 24-h mean arterial ambulatory pressure (MAP) and in nocturnal MAP decline between the two assessments were significant determinants of the differences in 24-h and symmetrical AASI values.

Conclusions: Although no differences were found in average AASI values of the two ambulatory recordings, significant differences were observed in their reproducibility, with 24-h AASI being the most reproducible measure in terms of all the examined criteria.American Journal of Hypertension 2010; doi:10.1038/ajh.2009.217.