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Table 2 Variation in DINAMAP™ measurements of arm and ankle systolic blood pressure and the ankle-brachial index

From: The reliability of the ankle-brachial index in the Atherosclerosis Risk in Communities (ARIC) study and the NHLBI Family Heart Study (FHS)

Estimate Ankle SBP Arm SBP ABI
Mean (SD) of pair means, mmHg* 146.2 (23.76) 125.2 (19.57) 1.178 (0.1522)
Mean (SD) of pair differences, mmHg* -3.1 (20.67) 0.9 (15.24) -0.031 (0.1494)
Square root of variance components, mmHg*    
   Between-person 21.4 (17.6,25.1) 18.0 (14.5, 1.3) 0.133 (0.112,0.150)
   Within-person 14.6 (12.7,16.5) 10.8 (8.9,12.4) 0.106 (0.091,0.121)
   Total 25.9 (22.8,28.7) 21.0 (18.3, 3.7) 0.170 (0.151,0.185)
Reliability coefficient 0.682 (0.570, 0.772) 0.736 (0.622, 0.827) 0.612 (0.505, 0.699)
Within-person coefficient of variation, % 10.0 (8.6, 11.2) 8.6 (7.1, 9.9) 9.0 (7.7, 10.2)
Pearson correlation coefficient 0.68 0.74 0.62
  1. *Systolic blood pressures (SBPs) in mmHg; the ankle-brachial index (ABI) is without units.
  2. Difference represents first minus second measure.
  3. Estimate (95% confidence interval).
  4. p < .05 for t-test of zero mean. Adjustment for the fixed effect of time changed very little the estimates of variance components.