Comparison of automated office blood pressure measurement with 24-hour ambulatory blood pressure measurement

Figures & data

Table 1. Automated office and ambulatory systolic and diastolic blood pressure values.

	Hypertension cohort (N = 135)	TIA cohort (N = 72)	p-Value
	Mean mm Hg (SD)	Mean mm Hg (SD)
SBP
AOBP 1-h average^c	134.5 (14.4)	124.4 (15.5)	<0.001
ABPM 24-h average^a	133.3 (13.6)	126.7 (15.0)	0.002
ABPM daytime average^b	137.6 (13.9)	130.0 (15.4)	<0.001
ABPM night-time average	124.4 (15.4)	119.6 (15.8)	0.033
DBP
AOBP 1-h average^c	78.8 (11.0)	73.1 (9.5)	<0.001
ABPM 24-h average^a	78.6 (9.5)	74.8 (10.2)	0.009
ABPM daytime average^b	82.0 (9.9)	77.7 (10.6)	0.004
ABPM night-time average	71.4 (10.3)	68.6 (10.7)	0.075

^aTarget level: SBP < 135 mm Hg DBP < 85 mm Hg; ^bTarget level: SBP < 130 mm Hg, DBP < 80 mm Hg; ^cTarget level: SBP < 135 mm Hg DBP < 85 mm Hg.

Given values are mean ± standard deviation. Bold values are statistically significant at alpha-level of 5%.

SBP: systolic blood pressure, DBP: diastolic blood pressure, SD: standard deviation, ABPM: ambulatory blood pressure measurement, AOBP: repeated unattended automated office blood pressure measurement, TIA: transient ischaemic attack, h: hour.

Table 2. General characteristics.

	Total (n = 207)	Hypertension cohort (n = 135)	TIA cohort (n = 72)	Significance (p-value)
Male, n (%)	120 (58.0%)	73 (49.3%)	47 (68.8%)	0.120
Age, year	57.9 (±12.0)	56.8 (±11.7)	59.7 (±12.5)	0.006
BMI, kg/m^2	26.9 (±5.5)	27.8 (±5.3)	25.6 (±5.8)	0.094
Smoking, n (%)	39 (18.8%)	19 (14%)	20 (27.7%)	<0.001
Previous CVD:	115 (55.6%)	43 (31.9%)	72 (100%)	<0.001
TIA or CVA	99 (47.8%)	27 (24.6%)	72 (100%)	<0.001
Coronary artery disease	34 (16.4%)	19 (14.1%)	15 (20.8%)	0.211
Peripheral artery disease	13 (6.3%)	8 (5.6%)	5 (6.9%)	0.774
Use of antihypertensive drugs, n (%)	166 (80.2%)	120 (88.9%)	55 (65.3%)	<0.001
Number of used antihypertensive drugs, n (%)
0	40 (19.3%)	15 (12.3%)	25 (31.3%)
1	63 (30.4%)	33 (24.4%)	30 (38.8%)
2	46 (22.2%)	36 (26.7%)	10 (21.3%)
≥3	58 (28.1%)	51 (37.8%)	7 (8.8%)

Given values are mean ± standard deviation or number (%).

BMI: body mass index, CVD: cardiovascular disease, TIA: transient ischaemic attack, CVA: cerebrovascular accident.

Figure 1. Bland–Altman plot for systolic blood pressure for (a) 1-h AOBP vs 24-h ABPM and (b) AOBP vs daytime ABPM. The average blood pressure values on the x-axis are the combined blood pressure averages of AOBP and ABPM.

Figure 2. Bland–Altman plot for diastolic blood pressure for (a) 1-h AOBP vs 24-h ABPM and (b) AOBP vs daytime ABPM. The average blood pressure values on the x-axis are the combined blood pressure averages of AOBP and ABPM.

Table 3. Binary logistic regression analysis with (dis)agreement as outcome.

	(Dis)Agreement based upon contrast
	AOBP vs 24-h ABPM	AOBP vs day mean 24-h ABPM	AOBP vs 24-h ABPM	AOBP vs day mean 24-h ABPM
	(Figure 1(A), SBP)	(Figure 1(B), SBP)	(Figure 2(A), DBP)	(Figure 2(B), DBP)
TIA (ref = hypertension)	0.26 (0.12–0.56)	1.12 (0.57–2.20)	0.48 (0.24–0.99)	0.93 (0.48–1.81)
Age	0.97 (0.94–0.99)	0.99 (0.96–1.01)	1.00 (0.98–1.03)	0.99 (0.96–1.01)
Male (ref = female)	1.25 (0.66–2.37)	0.85 (0.47–1.55)	1.42 (0.77–2.61)	1.17 (0.66–2.09)
BMI	0.95 (0.89–1.00)	0.93 (0.88–0.99)	1.00 (0.94–1.05)	0.94 (0.88–0.99)
Number of antihypertensive drugs
1 (ref. = 0)	2.54 (1.01–6.40)	2.26 (0.97–5.25)	1.75 (0.72–4.23)	1.70 (0.74–3.88)
2 (ref. = 0)	3.27 (1.12–9.55)	1.86 (0,69–5.00)	0.82 (0.30–2.21)	1.87 (0.71–4.98)
3 (ref. = 0)	3.36 (1.19–9.52)	1.82 (0.70–4.69)	0.94 (0.36–2.46)	2.07 (0.81–5.32)
n	205	205	205	205
−2 loglikelihood	246.16	273.17	263.23	280.71
Chi-square (df, p-value)	20.87 (7, 0.004)	9.61 (7, 0.21)	12.71 (7, 0.08)	3.47 (7, 0.84)
Nagelkerke R square	0.133	0.061	0.081	0.022

Note: Estimates are Odds Ratios (ORs) and 95% Confidence intervals (95% CI); Bold values are statistically significant at alpha-level of 5%; Cohort dummy consist of two groups: TIA and hypertension (reference category).

BMI: body mass index, AOBP: repeated unattended automated office blood pressure measurement, SBP: systolic blood pressure, DBP: diastolic blood pressure, TIA: transient ischaemic attack.

We used Δ > 10 mm Hg for SBP and Δ > 5 mm Hg for DBP as a cut-off for classifying patients as being in disagreement (coded as 0, agreement is coded as 1), this corresponds to the red and open dots as patients who are in disagreement in both Figures 1 and 2.