Accuracy of self-monitored blood pressure for diagnosing hypertension in primary care.
OBJECTIVE
To assess the diagnostic accuracy of recommendations for self-monitoring blood pressure (BP) for diagnosing hypertension in primary care.


METHODS
Two hundred and forty-seven consecutive participants with raised (≥130 mmHg systolic) BP measured by their general practitioner from four primary care practices in the United Kingdom underwent 28 days of self-monitoring followed by 24-h ambulatory BP monitoring (ABPM). Diagnostic accuracy of the first 7 days of self-monitored BP (minimum 4 days, discarding readings on day 1) in detecting hypertension with ambulatory blood pressure was taken as reference.


RESULTS
Two hundred and three participants were included, 109 (53.7%) of whom were diagnosed with hypertension using daytime ambulatory BP. The average of days 2-7 self-monitored BP correctly classified 150 of 203 participants [sensitivity 93.6%, 95% confidence interval (CI) 87.2-97.4%; specificity 51.1%, 95% CI 40.5-61.5%). However, the average of days 2-5 self-monitoring correctly classified 152 of 203 participants due to better specificity (53.2%, 95% CI 42.6-63.6%). In sensitivity analysis, diagnostic accuracy was not improved by inclusion of readings beyond day 5, and inclusion of readings taken on day 1 had no impact on diagnostic accuracy. Self-monitoring in the clinic was more accurate than readings taken by the general practitioner, but not self-monitoring outside of the clinic.


CONCLUSIONS
Hypertension can be ruled out in the majority of patients with elevated clinic BP using the average of the first 5 consecutive days of self-monitored BP, supporting lower limits for self-monitoring readings in current guidelines. Performing readings beyond day 5 and including readings taken on the first day had no clinical impact on diagnostic accuracy.
aNuffield Department of Primary Care Health Sciences, University of Oxford bNational Institute for Health Research School for Primary Care Research, Oxford, UK cDepartment of Family Medicine, University of Washington, Seattle, Washington, USA.
David
D
Nunan
Matthew
M
Thompson
Carl J
CJ
Heneghan
Rafael
R
Perera
Richard J
RJ
McManus
Alison
A
Ward
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001794:Blood Pressure; D001795:Blood Pressure Determination / Q000592:standards*; D018660:Blood Pressure Monitoring, Ambulatory; D015331:Cohort Studies; D005260:Female; D006801:Humans; D006973:Hypertension / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D011320:Primary Health Care; D011446:Prospective Studies; D012648:Self Care / Q000592:standards*; D012680:Sensitivity and Specificity; D006113:United Kingdom