How well do clinic-based blood pressure measurements agree with the mercury standard?
BACKGROUND
Obtaining accurate blood pressure (BP) readings is a challenge faced by health professionals. Clinical trials implement strict protocols, whereas clinical practices and studies that assess quality of care utilize a less rigorous protocol for BP measurement.


OBJECTIVE
To examine agreement between real-time clinic-based assessment of BP and the standard mercury assessment of BP.


METHODS
Prospective reliability study.


METHODS
One hundred patients with an International Classification of Diseases-9th edition code for hypertension were enrolled.


METHODS
Two BP measurements were obtained with the Hawksley random-zero mercury sphygmomanometer and averaged. The clinic-based BP was extracted from the computerized medical records.


RESULTS
Agreement between the mercury and clinic-based systolic blood pressure (SBP) was good, intraclass correlation coefficient (ICC)=0.91 (95% confidence interval (CI): 0.83 to 0.94); the agreement for the mercury and clinic-based diastolic blood pressure (DBP) was satisfactory, ICC=0.77 (95% CI: 0.62 to 0.86). Overall, clinic-based readings overestimated the mercury readings, with a mean overestimation of 8.3 mmHg for SBP and 7.1 mmHg for DBP. Based on the clinic-based measure, 21% of patients were misdiagnosed with uncontrolled hypertension.


CONCLUSIONS
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.
Kim
Jennifer W
JW
Duke University School of Medicine, Durham, NC, USA.
Bosworth
Hayden B
HB
Voils
Corrine I
CI
Olsen
Maren
M
Dudley
Tara
T
Gribbin
Matthew
M
Adams
Martha
M
Oddone
Eugene Z
EZ
D000046:Academic Medical Centers; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001794:Blood Pressure; D001795:Blood Pressure Determination / Q000592:standards*; D003951:Diagnostic Errors; D005260:Female; D006801:Humans; D006973:Hypertension / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D009657:North Carolina; D010044:Outpatient Clinics, Hospital; D011446:Prospective Studies; D012015:Reference Standards; D015203:Reproducibility of Results; D019722:Sphygmomanometers