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The normal difference in bilateral indirect blood pressure recordings in hypertensive individuals.

OBJECTIVE
If there is a significant dichotomy between bilateral systolic blood pressure determinations in both arms in hypertensive individuals, it is often taken as a sign of underlying pathology. The primary objective was to determine what the normal variation might be for a significant difference between blood pressures in both arms. A clinically significant difference was chosen as a systolic blood pressure value greater than 10 mm Hg between the upper extremities, as is commonly quoted at the bedside and in the literature.


METHODS
Bilateral indirect blood pressure determinations were obtained in 100 subjects with hypertension in the sitting position. The blood pressure was obtained by two observers, one the recorder and the other who obtained the blood pressure but was blinded to the actual values taken. The order of blood pressure determination in the first arm was determined prior to the study from a table of random numbers. The coefficient of variation in obtaining the blood pressure in each arm was determined in 5 of the 100 subjects. The age, sex, and handedness of each individual were recorded as demographic variables.


RESULTS
The average left and right systolic blood pressures were 139 +/- 22 and 141 +/- 22 mm Hg, respectively. The average left and right diastolic blood pressures were 78 +/- 12 and 79 +/- 13 mm Hg, respectively. There was no significant difference between left minus right systolic or diastolic differences (paired t-test). There was no significant difference between systolic or diastolic blood pressures between gender or between left- and right-handed individuals (nonpaired t-test). The average coefficients of variation for taking right and left arm systolic pressures were 2.90% and 1.32%, respectively. Eighteen subjects (18%) had differences in systolic blood pressure between both arms exceeding 10 mm Hg (10% to 26%, 95% confidence interval).


CONCLUSIONS
Differences of more than 10 mm Hg in indirect systolic blood pressure recordings between arms are frequent in asymptomatic hypertensive individuals and do not per se indicate any pathologic condition. In the right clinical situation, differences that are noted should be repeated and should be added to the total clinical picture when used to determine whether a pathologic condition is present. Assuming no significant aortic or subclavian disease in the population tested, the specificity of the bilateral blood pressure test was 82%.