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Home Blood Pressure Monitors Are Wrong 70 Percent of the Time, Says Study (arstechnica.com)

Posted by BeauHD on from the six-of-one-half-a-dozen-of-the-other dept.

An anonymous reader quotes a report from Ars Technica: In a study out this week, about 70 percent of home blood-pressure devices tested were off by 5 mmHg or more. That's enough to throw off clinical decisions, such as stopping or starting medication. Nearly 30 percent were off by 10 mmHg or more, including many devices that had been validated by regulatory agencies. The findings, published in The American Journal of Hypertension, suggest that consumers should be cautious about picking out and using such devices -- and device manufacturers need to step up their game. Lead author Raj Padwal and his colleagues set out to test the accuracy of the devices themselves. Funded by the University of Alberta Hospital Foundation, they compared the home blood-pressure monitors of 85 patients with a gold-standard blood-pressure measurement technique. The patients' monitors varied by type, age, and validation-status. But they all used an automated oscillometric method, which measures oscillations in the brachial artery and uses an algorithm to calculate blood pressure. The gold-standard method was the old-school auscultatory method, which involves the arm-squeezing sphygmomanometer and a clinician listening for thumps with a stethoscope. Of the 85 home devices, 59 were inaccurate by 5 mmHg or more in either their systolic (the top number that's the maximum pressure of a heart beat) or diastolic (the bottom number that's the minimum between-beat pressure). That's 69 percent inaccurate. Of those, 25 (or 29 percent) were off by 10 mmHg or more. And six devices (seven percent) were off by 15 mmHg or more.

3 of 90 comments (clear)

  1. Duh! by nospam007 · · Score: 5, Informative

    The ones done by doctors are off as well, it's called 'white coat hypertension'.
    They might prescribe medication just because you're afraid of him.

    http://www.bloodpressureuk.org...

  2. Clinicians are probably just as inaccurate by Dan+East · · Score: 4, Informative

    As a former EMT-Cardiac, and having worked in a number of emergency departments, I can say that the blood pressure obtained by many clinicians is off by more than that, and I'll explain why. When using a sphygmomanometer and auscultating for blood to begin flowing through the veins, on the systolic (the first number / highest pressure value) you will only hear the sound of the blood flow on the heart beat. So the rate in which you are letting air out of the cuff determines the accuracy, and further, the slower the patient's heartrate, the greater the inaccuracy will be.

    So let's say they are letting air out of the cuff at 20 mmHg per second (thus from full inflation at 200 mmHg to a normal diastolic of 70 it would be 130 mmHg = 6.5 seconds), and a patient's heartrate is 60 beats per minute. The heart is beating once each second and the needle is moving 20 mmHg per second, thus the number they see when the heart beats could be as much as 20 mmHg lower than the actual blood pressure. I'm sure you have had nurses take your blood pressure and they took way less than 6.5 seconds to measure it - in that case the error margin would be even greater.

    For the systolic value the inaccuracy will be a lower value than actual, and for the diastolic the inaccuracy will result in a higher value than actual.

    --
    Better known as 318230.
  3. Clinical decisions? by thegarbz · · Score: 3, Informative

    Just who makes clinical decisions on a 10mmHg spot measurement?

    a) home blood pressure readings aren't used to make clinical decisions.
    b) doctor blood pressure readings aren't used in isolation to make clinical decisions.
    c) one off blood pressure readings aren't used to make clinical decisions.
    d) doctors manually taking readings are likely to be off by more than 10mmHg.
    e) depending on the time of the day your blood pressure readings are likely to be off by more than 10mmHg.
    f) depending on which arm you take the reading from will affect your by 3-10mmHg.
    g) depending on how long you've been sitting in the chair at the doctors office will affect your reading by 3-10mmHg

    I still remember my last doctors visit. The doctor looked shocked and said I have hypertension. Then he told me to sit and relax a for a while. We did some other checks, then back to blood pressure. Well I fell 11mmHg down to pre-hypertension. He said to come back 3 times a week for the next 2 weeks preferably at the same time of day. Final diagnosis: Bloodpressure was normal.