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Clinical Question:
How well do blood pressure measurements taken in the office correlate with a
gold standard in-office measurement?
Bottom Line:
In this study, usual blood pressure readings in an office were frequently
higher a standardized measurement, leading to incorrect labeling of blood
pressure control in 1 of 5 patients.Health professionals should be aware of
this potential difference when utilizing clinic-based BP values for making
treatment decisions and/or assessing quality of care.
Reference:
How well do clinic-based blood pressure measurements agree with the mercury
standard?
Kim JW, Bosworth HB, Voils CI, Olsen M, Dudley T, Gribbin M, Adams M, Oddone
EZ.J Gen Intern Med. 2005 Jul;20(7):647-9.
Study Design:
Diagnostic test evaluation
Funding:
Government
Setting:
Outpatient (primary care)
Synopsis:
The researchers conducting this study compared the blood pressure
measurements recorded during a visit to an internal medicine clinic with
those obtained from the same patients by a trained research assistant. Using
a convenience sample of 100 patients, most of whom were taking
antihypertensives, the researchers measured blood pressure either before the
clinic visit or immediately afterward, on average approximately 24 minutes
within the time of the clinic reading. The researchers were carefully
trained and performed all the measurements according to the book; proper
cuff size, arm at heart level, patients resting for 5 minutes, air pressure
released slowly. They used a mercury sphygmomanometer with a random zero,
meaning that the blood pressure numbers they obtained on the patients were
not real but had to be converted to the real number by subtracting a number
that was unique to each measurement. This research tool is designed to
prevent blood pressure readings to be read where the researcher thinks the
number should be. The clinic blood pressure measurements were performed by
the office nurse. Overall, the agreement between the measurements on
individual patients was good, with an intraclass correlation coefficient of
.91 (95% CI, 0.62 - 0.86). However, using the degree of agreement statistic,
clinic-based measurements were 8.3 mm Hg systolic and 7.1 mm Hg diastolic
higher than the standard. A possible clinical impact, due to
misclassification of blood pressure, could have occurred in 21% of patients
who had controlled blood pressures as measured by the researcher but were
uncontrolled according to the clinic measurement. The degree of
overestimation more commonly occurred when blood pressures were in the
normal range. |