Reproducibility of the ambulatory arterial stiffness index in hypertensive patients.
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.
Dechering
Dirk G
DG
Department of General Internal Medicine, University Medical Centre St Radboud, Radboud University, Nijmegen, The Netherlands.
van der Steen
Marijke S
MS
Adiyaman
Ahmet
A
Thijs
Lutgarde
L
Deinum
Jaap
J
Li
Yan
Y
Dolan
Eamon
E
Akkermans
Reinier Pm
RP
Richart
Tom
T
Hansen
Tine W
TW
Kikuya
Masahiro
M
Wang
Jiguang
J
O'brien
Eoin
E
Thien
Theo
T
Staessen
Jan A
JA
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