Table 2.

Mean Difference in Blood Pressure Measurements by Random-zero and Standard Mercury Sphygmomanometers

	Systolic, mm Hg		Diastolic, mm Hg
Reading No.
	Mean ± SD	Mean Difference (95% CI)	Mean ± SD	Mean Difference (95% CI)
Overall
1st
Random-zero	117.7 ± 15.5	−3.1 (−3.4, −2.7) **	73.6 ± 11.2	−1.3 (−1.6, −1.0) **
Standard	120.7 ± 15.8		75.0 ± 11.1
2nd
Random-zero	117.2 ± 15.5	−2.8 (−3.1, −2.4) **	73.7 ± 11.1	−1.0 (−1.3, −0.6) **
Standard	120.0 ± 15.7		74.7 ± 11.1
3rd
Random-zero	116.9 ± 15.3	−2.7 (−3.0, −2.3) **	73.6 ± 10.9	−0.9 (−1.2, −0.6) **
Standard	119.6 ± 15.6		74.5 ± 11.0
Men
1st
Random-zero	119.2 ± 14.1	−2.8 (−3.2, −2.3) **	75.3 ± 10.7	−1.3 (−1.8, −0.9) **
Standard	122.0 ± 14.5		76.6 ± 10.8
2nd
Random-zero	118.8 ± 14.0	−2.5 (−3.0, −2.1) **	75.5 ± 10.5	−1.0 (−1.5, −0.6) **
Standard	121.3 ± 14.5		76.5 ± 10.8
3rd
Random-zero	118.3 ± 13.9	−2.7 (−3.1, −2.2) **	75.4 ± 10.6	−1.0 (−1.5, −0.6) **
Standard	121.0 ± 14.4		76.4 ± 10.7
Women
1st
Random-zero	116.0 ± 16.9	−3.4 (−4.0, −2.9) **	71.8 ± 11.4	−1.4 (−1.8, −0.8) **
Standard	119.4 ± 17.1		73.2 ± 11.2
2nd
Random-zero	115.5 ± 16.8	−3.0 (−3.6, −2.5) **	71.8 ± 11.3	−0.9 (−1.3, −0.4) *
Standard	118.5 ± 16.9		72.7 ± 11.1
3rd
Random-zero	115.3 ± 16.6	−2.8 (−3.3, −2.2) **	71.8 ± 10.9	−0.7 (−1.1, −0.3) *
Standard	118.1 ± 16.8		72.5 ± 10.9

SD = standard deviation; CI = confidence interval.

^*p<0.01,

^**p<0.0001 for comparisons between blood pressure values using the random zero sphygmomanometer vs. standard mercury sphygmomanometer.