Community-based blood pressure measurement by non-health workers using electronic devices: a validation study

Figures & data

Table 1. Summary statistic for systolic and diastolic blood pressure in mmHg, measured with mercury and electronic devices at four different times (T1–T4)

Measure	Summary statistic
	Max	Min	Median	Mean	SD	n
Systolic
Mercury (T1)	181	89	124	128	22	55
Electronic (T2)	193	99	125	127	21	55
Mercury (T3)	177	92	127	124	19	54
Electronic (T4)	200	95	125	126	22	54
Diastolic
Mercury (T1)	111	50	80	81	13	55
Electronic (T2)	98	58	75	75	10	55
Mercury (T3)	100	56	79	79	11	54
Electronic (T4)	95	55	74	73	10	54

Fig. 1.  Bland–Altman plots of the blood pressure differences between each possible pair of device-operator combination: (a) diastolic pressure and (b) systolic pressure. The solid horizontal line indicates the mean difference between the measures, the dashed horizontal lines indicate the 95% limits of agreement.

Fig. 2.  Ogives showing the proportion (y-axis) of blood pressure measures with an absolute difference of no more than a certain pressure (x-axis) for three of the four possible pairs of device-operator combinations.

Table 2. The null, full and reduced, mixed-effects linear models of blood pressure measurement

	Null		Full		Reduced
	Estimate	95%HPD	Estimate	95%HPD	Estimate	95%HPD
Systolic models
Time 2 (electronic)			−0.002	−.038 to 0.029	−0.002	−0.04 to 0.028
Time 3 (mercury)			−0.026	−0.062 to 0.006	−0.027	−0.061 to 0.007
Time 4 (electronic)			−0.011	−0.045 to 0.022	−0.01	−0.047 to 0.02
Age (centre = 49)			0.006*	0.004 to 0.008	0.005***	0.004 to 0.007
Sex (female)			−0.012	−0.062 to 0.033
Diabetes (yes)			−0.006	−0.057 to 0.049
Hypertension (yes)			−0.038	−0.090 to 0.026
Intercept	4.8***	4.80–4.85	4.9***	4.86–4.91	4.8***	4.81–4.87
AIC	−428.8		−441		−446.4
σ ^2 Person (level 2)	0.022		0.016		0.016
σ ^2 Resid	0.003		0.003		0.003
Diastolic models
Time 2 (electronic)			−5.1***	−8.1 to −2.7	−5.1***	−2.9 to −8.1
Time 3 (mercury)			−1.2	−4.2 to 1.2	−1.2	−4.3 to 1.1
Time 4 (electronic)			−6.8***	−7.1 to −9.9	−6.8***	−10.0 to −4.6
Age (centre = 49)			0.3***	0.1–0.3	0.2*	0.09
Sex (female)			−3.3	−7.1 to 0.5
Diabetes (yes)			1.4	−2.4 to 5.7
Hypertension (yes)			−4.3	−8.5 to 0.5
Intercept	77.0***	74.9 − 76.8	83.6***	78.2–82.9	80.4***	80.4–80.5
AIC	1533		1480		1477
σ ^2 Person (level 2)	105.1		91.6		96.2
σ ^2 Resid	33.2		23.2		23.2

*p<0.05, ***p<0.001 based on MCMC estimation.