A study published in the American Journal of Hypertension reported that 70% of readings from home blood pressure (BP) monitors are inaccurate, which may lead to serious health outcomes if used for decision-making. 

Researchers from the University of Alberta aimed to examine the accuracy of home BP devices vs. auscultatory reference standard BP measurements. The study included 85 individuals aged 18 years and older who owned an oscillometric home BP device (wrist or upper-arm) with levels between 80–220/50–120mmHg with an arm circumference between 25–43cm. Patients who were pregnant or who had atrial fibrillation were excluded from the analysis.

Researchers compared readings from the subject’s home BP monitor to simultaneous 2-observer auscultation using a mercury sphygmomanometer. They assessed the proportion of patients with device-to-auscultatory differences of ≥5, 10, and 15mmHg as well as predictors of systolic and diastolic BP differences. 

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Of the total patients, 78% had hypertension and the mean arm circumference was 32.7±3.7cm. The mean BPs recorded by home BP devices were 125.7±14.0/73.9±10.4mmHg vs. 129.0±14.7/72.9±9.3 for auscultation (difference -3.3±7.3/0.9±6.1; P<0.0001 for systolic and P=0.17 for diastolic). The proportion of devices with systolic or diastolic BP differences from auscultation was 69% for ≥5mmHg, 29% for 10mmHg, and 7% for 15mmHg.  

Study authors observed that higher arm circumference was a statistically significant predictor of having higher systolic BP (P=0.004) and diastolic BP (P=0.03).

The mean differences from the 2-observer auscultation were “acceptable,” but when tested on their owners, most of the home devices were inaccurate by ≥5mmHg. Lead author, Jennifer S. Ringrose, stated that, “Ensuring acceptable accuracy of the device-owner pairing should be prioritized.”

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