Failure of the community-based Vita-Stat automated blood pressure device to accurately measure blood pressure
B. L. Whitcomb, A. Prochazka, M. LoVerde and R. L. Byyny
Division of Internal Medicine, University Hospital, Denver, USA.
OBJECTIVE: To evaluate the Vita-Stat automated blood pressure computer (a
patient-operated blood pressure measuring device available in the
community) to determine its value as an instrument to monitor blood
pressure in the ambulatory patient. DESIGN: Comparative study using the
Vita-Stat vs a gold standard, the mercury sphygmomanometer. SETTING: Three
local grocery stores. PARTICIPANTS: Sixty-three passersby who agreed to
answer questions and to sit for several measurements of blood pressure.
INTERVENTIONS: Simultaneous measurement of blood pressure with each subject
wearing a Vita-Stat cuff on the left arm and a mercury sphygmomanometer
cuff on the right arm. Two pressures were measured sequentially in the same
manner. MAIN OUTCOME MEASURES: The reproducibility, accuracy, sensitivity,
and specificity of the Vita-Stat computer compared with the gold standard.
RESULTS: In sequential measurements, the Vita-Stat readings of both
systolic and diastolic blood pressure correlated less well with each other
than did the mercury readings (intramachine differences). The Vita-Stat
readings also correlated poorly with the mercury readings of systolic and
diastolic blood pressure (intermachine differences). The variability in
readings recorded by the Vita-Stat were striking, with differences of up to
60 mm Hg from the mercury readings. More than half (63.2%) of the subjects
had Vita-Stat readings that were more than 5 mm Hg different from the
mercury readings. Vita-Stat systolic readings were usually lower than
mercury readings and also varied by as much as 60 mm Hg below in one
patient to 58 mm Hg above the mercury reading in another. The sensitivity
of the Vita-Stat in correctly diagnosing hypertension was 0.26; the
negative predictive value was 0.45. CONCLUSIONS: Our data suggest that the
Vita-Stat is not only inconsistent but inaccurate in measuring blood
pressure in the ambulatory patient and is, therefore, not appropriate to
use as a monitoring device.
