Number of measurement days needed for obtaining a reliable estimate of home blood pressure and hypertension status

Figures & data

Figure 1. Mean home blood pressure (BP) during the current European guideline-based 7-day HBPM protocol (2 measurements per day).

Table 1. Characteristics of the study population. All data in n (%) or mean ± standard deviation.

	n = 567
Age (years)	62 ± 14
Male sex	299 (53%)
Healthcare domain
General practice	373 (82%)
Hospital	82 (18%)
Home blood pressure measurement
Systolic blood pressure (mmHg)	143 ± 16
Morning systolic blood pressure (mmHg)	142 ± 17
Evening systolic blood pressure (mmHg)	144 ± 17
Diastolic blood pressure (mmHg)	84 ± 10
Morning diastolic blood pressure (mmHg)	84 ± 10
Evening diastolic blood pressure (mmHg)	84 ± 10
Heart rate (beats/min)	71 ± 10
Morning heart rate (beats/min)	69 ± 10
Evening heart rate (beats/min)	73 ± 10

Figure 2. Maximal deviation from home blood pressure of an increasing number of successive home BP readings for 95% of individuals. Positive deviation calculated as 1.96 × standard error of average BP + systematic bias of average BP. Negative deviation calculated as −1.96 × standard error of average BP − systematic bias of average BP.

Figure 3. Maximal deviation from home blood pressure of an increasing number of successive home BP readings for 95% of individuals with (blue circles), and without (red squares) BP readings taken on day 1. Positive deviation calculated as 1.96 × standard error of average BP + systematic bias of average BP. Negative deviation calculated as −1.96 × standard error of average BP − systematic bias of average BP.

Figure 4. Agreement of home hypertension status is determined with an increasing number of successive BP readings expressed by the kappa (ĸ) statistic. Home hypertension: Mean home systolic blood pressure (BP) ≥135 mm Hg or home diastolic BP ≥85 mm Hg. Good agreement: 95% lower confidence limit (LCL) of the κ statistic ≥0.80.

Table 2. Agreement between the increasing number of successive home BP measurements and the current 7-day HBPM protocol for the diagnosis of home hypertension (mean home systolic BP ≥135 mm Hg and/or mean home diastolic BP ≥85 mm Hg).

No. of measurements	Kappa statistic (95%CI)	Sensitivity (95%CI)	Specificity (95%CI)	Positive predictive value (95%CI)	Negative predictive value (95%CI)
1	0.61 (0.52–0.70)	0.94 (0.91–0.96)	0.64 (0.54–0.73)	0.88 (0.85–0.92)	0.78 (0.68–0.86)
2	0.63 (0.54–0.72)	0.95 (0.92–0.97)	0.63 (0.53–0.73)	0.88 (0.84–0.92)	0.82 (0.71–0.90)
3	0.69 (0.60–0.77)	0.96 (0.93–0.98)	0.68 (0.58–0.77)	0.90 (0.86–0.93)	0.86 (0.76–0.93)
4	0.70 (0.62–0.79)	0.96 (0.93–0.98)	0.70 (0.60–0.79)	0.90 (0.86–0.93)	0.86 (0.76–0.93)
5	0.76 (0.69–0.84)	0.97 (0.94–0.99)	0.75 (0.65–0.83)	0.92 (0.88–0.95)	0.90 (0.81–0.96)
6	0.80 (0.72–0.87)	0.98 (0.95–0.99)	0.78 (0.68–0.86)	0.92 (0.89–0.95)	0.93 (0.84–0.97)
7	0.83 (0.76–0.90)	0.97 (0.94–0.99)	0.84 (0.75–0.91)	0.94 (0.91–0.97)	0.91 (0.83–0.96)
8	0.86 (0.79–0.92)	0.98 (0.96–1.00)	0.84 (0.75–0.91)	0.94 (0.91–0.97)	0.95 (0.88–0.99)
9	0.89 (0.84–0.95)	0.99 (0.97–1.00)	0.88 (0.80–0.94)	0.96 (0.93–0.98)	0.96 (0.90–0.99)
10	0.90 (0.85–0.95)	0.99 (0.96–1.00)	0.89 (0.81–0.95)	0.96 (0.93–0.98)	0.96 (0.90–0.99)
11	0.92 (0.88–0.97)	0.99 (0.97–1.00)	0.91 (0.83–0.96)	0.97 (0.94–0.99)	0.98 (0.92–1.00)
12	0.97 (0.94–1.00)	1.00 (0.98–1.00)	0.96 (0.89–0.99)	0.98 (0.96–1.00)	1.00 (0.96–1.00)
13	0.97 (0.94–1.00)	0.99 (0.97–1.00)	0.98 (0.92–1.00)	0.99 (0.97–1.00)	0.98 (0.92–1.00)
14	1.00 (1.00–1.00)	1.00 (0.98–1.00)	1.00 (0.96–1.00)	1.00 (0.98–1.00)	1.00 (0.96–1.00)

Data availability statement

The data that support the findings of this study are available from the corresponding author, WS, upon reasonable request.