TIME-WEIGHTED VS CONVENTIONAL QUANTIFICATION OF 24 HOUR AVERAGE AMBULATORY SYSTOLIC BLOOD PRESSURE (original) (raw)

Abstract

Background Conventional calculation of mean 24-h ambulatory blood pressure (BP), SBP and DBP based on the average of all BP readings disregards the fact that a larger number of measurements is usually scheduled during the daytime than at night, an imbalance possibly leading to an overestimation of 24-h average BP. The aim of our study was to quantify this possible bias and to explore its determinants.

Figures (9)

Table 1 Number of blood pressure readings for the daytime, the night-time and the 24-h period, and the day/night ratio of such numbers Values are expressed as mean+ SD, with the addition of the range betweer maximum and minimum number of readings for each of the three groups con sidered in our study. 24-h D/N ratio, ratio between 24-h daytime and night-time measurements.

Table 1 Number of blood pressure readings for the daytime, the night-time and the 24-h period, and the day/night ratio of such numbers Values are expressed as mean+ SD, with the addition of the range betweer maximum and minimum number of readings for each of the three groups con sidered in our study. 24-h D/N ratio, ratio between 24-h daytime and night-time measurements.

Bland-Altman analysis of the differences between 24-h blood pressures obtained by conventional and time-weighted analysis. Top panels: group |; intermediate panels: group II; bottom panels: group Ill. Left panels and black circles: 24-h SBP. Right panels and white circles: 24-h DBP. Solid line in each panel: mean value of overestimation bias. Dotted lines: 2SD over and under mean. BP, blood pressure.

Bland-Altman analysis of the differences between 24-h blood pressures obtained by conventional and time-weighted analysis. Top panels: group |; intermediate panels: group II; bottom panels: group Ill. Left panels and black circles: 24-h SBP. Right panels and white circles: 24-h DBP. Solid line in each panel: mean value of overestimation bias. Dotted lines: 2SD over and under mean. BP, blood pressure.

Correlation between nocturnal dip and calculated ‘bias’. Superior panels: group |; intermediate panels: group Il; lower panels: group Ill. Left panels and black circles: 24-h SBP. Right panels and white circles: 24-h DBP. Inserts in each panel: correlation coefficients and their statistical significance. NS, not significant.

Correlation between nocturnal dip and calculated ‘bias’. Superior panels: group |; intermediate panels: group Il; lower panels: group Ill. Left panels and black circles: 24-h SBP. Right panels and white circles: 24-h DBP. Inserts in each panel: correlation coefficients and their statistical significance. NS, not significant.

DF, degree of freedom; MS, Mean Square; SS, Sum of Squares. ANOVA, analysis of variance.

DF, degree of freedom; MS, Mean Square; SS, Sum of Squares. ANOVA, analysis of variance.

Correlations between total day/night ratio in number of readings and calculated ‘bias’. Superior panels: group |; intermediate panels: group Il; lower panels: group Ill. Left panels and black circles: 24-h SBP. Right panels and white circles: 24-h DBP. Insertions in each panel: correlation coefficients and their statistical significance. NS, not significant.

Correlations between total day/night ratio in number of readings and calculated ‘bias’. Superior panels: group |; intermediate panels: group Il; lower panels: group Ill. Left panels and black circles: 24-h SBP. Right panels and white circles: 24-h DBP. Insertions in each panel: correlation coefficients and their statistical significance. NS, not significant.

Degrees of freedom 447. Overestimation bias: SBP Addendum

Degrees of freedom 447. Overestimation bias: SBP Addendum

Overestimation bias: DBP

Overestimation bias: DBP

Degrees of freedom 447.

Degrees of freedom 447.

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