Become a fan of Slashdot on Facebook

 



Forgot your password?
typodupeerror
Medicine Software Science Hardware

Home Blood Pressure Monitors Are Wrong 70 Percent of the Time, Says Study (arstechnica.com) 90

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.
This discussion has been archived. No new comments can be posted.

Home Blood Pressure Monitors Are Wrong 70 Percent of the Time, Says Study

Comments Filter:
  • Duh! (Score:5, Informative)

    by nospam007 ( 722110 ) * on Friday June 09, 2017 @05:20PM (#54587827)

    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... [bloodpressureuk.org]

    • Signed in just to say pretty much what you already have. It's a very imprecise measure.
    • That's true. My blood pressure goes up when I'm at my doctor's office, but is normal everywhere else. I use two different electronic blood pressure monitors and they are fairly accurate. The one the doctor uses is just one of those around-the-wrist types (same brand as my two - Omron) and it's no more accurate than my around-the-upper-arm ones.

      I also have one of the arm-squeezing sphygmomanometers, but it's almost impossible to use one on yourself because you can hear the "thump thump" over a greater range
      • by tlhIngan ( 30335 )

        That's true. My blood pressure goes up when I'm at my doctor's office, but is normal everywhere else. I use two different electronic blood pressure monitors and they are fairly accurate. The one the doctor uses is just one of those around-the-wrist types (same brand as my two - Omron) and it's no more accurate than my around-the-upper-arm ones.

        My doctor thought the same as well - I kept measuring borderline with him and my pulse raced. So he set me up on a bed lying down with an automated machine that will

        • If it changes so much, what is actually supposed to be the threshold for intervention? The maximum? The top decile? The median? The average? The long-term rest value?
    • or the Tight White Coat Syndrome of the hot doctor
    • I have a foot problem and every time I go to see a physician I have a nurse escort me down this long hallway (maybe not so long really but MY FEET HURT) to check my weight. After I get weighed I go further down the hall to an office where I am sat down and the nurse asks me about all kinds of different diseases I could have (but likely don't, but now I'm thinking if I really do). At about this point I get my blood pressure, pulse rate, and temperature taken. My blood pressure almost always reads high. S

      • by Qzukk ( 229616 )

        Sounds like what I get at a regular doctor, so it seems my tax dollars are worth exactly as much as my own earned dollars.

        • Then maybe you need to put those take home dollars towards a different clinic. You have more choices than I do. With the VA I can take their care or leave it, by leaving it I have to pay for it with my tax dollars AND still have to pay for private care. You can shop for a different clinic with your money if you are not happy.

          It also bothers me that you are so forgiving of your tax money going towards second rate care.

          • Only if it is in network for a PPO or in my case with my crapsurance, only my primary care physician unless I get a referral. And I'm paying 8 grand a year with a 6500 deductible, so even with my PCP doing the work, I am STILL paying out of pocket.

            • I have experienced care from the private, public, and VA. I was at Togus, just a couple of days ago. I suspect they complain because they haven't seen the alternative. The VA does very, very well, even when compared internationally.

    • Aside from what you just said:

      To get the most accurate reading at your next blood pressure screening, insist the procedure be done properly. Follow these tips:

      * Do not exercise or eat for 30 minutes before having your blood pressure taken. (Even a cup of coffee can affect readings for several hours after you drink it.)
      * Rest at least five minutes beforehand. You should feel comfortable and relaxed in your surroundings.
      * Have your reading taken in the morning because biological rhythms naturally cause pressures to be higher in the afternoons and evenings.
      * Remove all clothing from the waist up. Just rolling up your shirtsleeve can act like a tourniquet and cause false readings.
      * Ask that your blood pressure include readings taken while you are lying, sitting, and standing. Readings often skyrocket as you change positions, which may signal weak adrenal glands—not high blood pressure.
      * Make sure your elbow is at the same level as your heart. Every doctor and nurse is taught this, but very few check it. An elbow that is even a couple of inches below the heart can make the reading as much as 17 points higher than it should be. There's no telling how many people have "low elbow" instead of high blood pressure!

      Source: https://www.drdavidwilliams.co... [drdavidwilliams.com]

      And yes, they did seem to take some precautions:

      For each study participant, the researchers took nine sequential blood pressure readings, switching between using the standard auscultatory method and the home monitors. For the auscultatory method, the researchers had two trained health professionals involved in the measurement, one taking it and another observing. If they disagreed on a measurement by more than 4 mmHg, they tossed the data and took the measurement again. With breaks in between each reading, the whole process usually took about 45 minutes per patient.

      But if they were allowed to throw out results, then it doesn't bode well for when my doctor does it either. My own personal doctor doesn't have multiple people taking my blood pressure multiple times, observing each other, double-checking their results, and throwing out results that vary too much.

      • by arth1 ( 260657 )

        Do not exercise or eat for 30 minutes before having your blood pressure taken. (Even a cup of coffee can affect readings for several hours after you drink it.)

        I have wondered about this. If my normal state of being is having traces of blood in my caffeine stream, wouldn't it be more valuable to know what my normal is than a state I'm never in?
        Likewise for exercise junkies - if they live their life on the burn, isn't that what makes the most sense to measure?

        • Yes, they're making all kinds of assumptions.

          That being said, if you're an active runner, your heart probably doesn't beat that much faster after a run than when you're resting. The same goes for caffeine. The more you consume caffeine, the less effect it will have on you.

        • This is why what's really wanted is a fitness tracker-like device which can also accurately measure your blood pressure. Then it can tell you what your blood pressure is when you get specified amounts of activity.

          I, for one, would really like sensors in my bloodstream that I could use to monitor salinity and blood sugar. And if I thought about it more, probably a whole bunch of other stuff. I've always imagined the readouts as some kind of electronic tattoo.

    • And told me to get a home unit, and bring it in to test it. His assessment differed from this in that he said that "most home blood pressure monitors are accurate". I brought in mine, the nurse tested it, and said it was accurate. The readings weren't 100% the same as what she got, but then they normally vary second to second anyhow.

      Also of note is that she was much more careful with the test when testing my unit as opposed to normal. For both their and my unit she had me sit quiet and still, she made sure

  • 5mm Hg error (Score:4, Interesting)

    by CrimsonAvenger ( 580665 ) on Friday June 09, 2017 @05:32PM (#54587933)

    Hmm, normal blood pressure is lt. 120mm Hg / lt. 80mm Hg.
    So, we're talking a 4% error, which will only matter if you're within that 4% of a breakpoint.

    Can't see this as a really big deal. I expect my blood glucose widget has a similar (if not larger) error factor, which might mean that I take an extra unit of Humalog (or take a unit less than I should) from time to time. Won't kill me....

    • by Bovius ( 1243040 )
      The 5mm Hg error isn't...too terribly bad, but 10mm Hg error or higher is unconscionable.

      I don't think looking at it as 4% error is the most useful comparison. It might be better to compare the error with the distance between different blood pressure categories [webmd.com], which is generally a 20 mm Hg jump for systolic, or 10 for diastolic.

      Someone with hypertension problems (i.e. the kind of person that might have a blood pressure cuff at home) would care quite a bit about an error of 10 mm Hg.
      • The 5mm Hg error isn't...too terribly bad, but 10mm Hg error or higher is unconscionable.

        Nope it's not. No one would base a clinical decision on a single measurement of 10mm Hg. While we're at it no one decides if they will take their medication based on a spot reading either.

        10mm Hg is still well within a margin of variability throughout a given day, and is still better than the variability of having two different doctors using stethoscopes to manually take the reading.

        Blood pressure is hard to measure.

  • I told my doctor that my blood pressure was higher when I lean forward than if I am reclined back.

    He didn't believe me until he took the measurements in his office.

    Turns out body position makes a statistical difference in your blood pressure readings:

    https://www.ncbi.nlm.nih.gov/p... [nih.gov]

    I took both of my BP meters in to the doctor's office and compared their readings with the doctor's readings. That way I know how much deviation to expect when taking measurements.

    • I took my machine to the doctor's office once to see how accurate it was. Two or three machines in the office kept reading higher than mine. I insisted on having a nurse take it by hand and that one matched my machine almost exactly. They claimed their office machines were calibrated periodically.
  • by religionofpeas ( 4511805 ) on Friday June 09, 2017 @05:40PM (#54587987)

    Home Blood Pressure Monitors Are Wrong 70 Percent of the Time, Says Study

    So, take 10 measurements, and look for the 3 identical ones.

    • If you put your elbow below your heart each time, then it doesn't matter if the results are identical. Your results will be wrong each time.

  • by mveloso ( 325617 ) on Friday June 09, 2017 @05:43PM (#54588017)

    Why don't they give us the most accurate devices?

    They don't even put the data anywhere, so we can't even figure it out for ourselves.

    It's 2017 people.

    • by mhkohne ( 3854 )

      Probably because it's a rather small sampling - 85 patients according to the abstract, which means they probably had only a small number of each individual device, and they can't be sure whether the devices are inaccurate due to their design, or whether there's some kind of handling problem that made them become inaccurate over time.

      • by mveloso ( 325617 )

        It was enough data to make a conclusion, which means it's good enough to publish the list as well as the article.

  • Being +/- 5mm Hg on a measurement of 140 mm is +/- 3.5%, but how accurate are the thresholds for treatment? A guideline may say that 140mm Hg needs treatment, but what is the error bar in that value? I bet it far exceeds 3.5% because of individual variation.

    And more than accuracy, I'd think that being precise would be more useful to a home user -- knowing that your BP increased by 7mm over a year sounds more useful than knowing that it's close to some arbitrary value.

  • My home blood pressure meter was more consistent than most of the doctor measurements I have received.

    • But is it accurate?

    • My dentist uses the same one I have at home. Now ask me why my dentist takes my blood pressure - I don't know.

      • Your dentist takes BP because many patients see a dentist much more often than they see a physician. If a dentist finds your BP is high he will suggest you let your physician know about it. Also, depending on the procedures he/she is planning to do, the BP is a go/no-go type measurement.

        • Despite saying I had no idea, I always really thought it was too yet to catch sleep apnea symptoms and offer an oral appliance.

      • I was curious why my dentist started taking BP, he said that insurance requires him to verify normal BP before being covered for certain procedures.
  • by jediborg ( 4808835 ) on Friday June 09, 2017 @05:55PM (#54588081)
    I've been using a home blood pressure monitor kit to monitor my bp for two years. Been working real hard to bring my high blood pressure down. Recently felt success when my doc told me it was significantly reduced.

    Now i don't know what to believe anymore
  • by Anonymous Coward

    As your doctor gets older your blood pressure will go down because your doctor's hearing will get worse. A good automated machine should be able to do better than a human.

  • by Anonymous Coward

    This is my world.

    The wrist ones are crap. Extrapolate to the finger one yourself...

    The GOLD STANDARD is only calibrated to within +/- 2mm.....ASSUMING they used a mercury unit, they did NOT specify this it seems.
    An typical manual aneroid sphyg is rarely maintained to even that level. They give no detail on their base unit, it could be off.

    Being off a few is normal.

    9 readings in 45 min is using the bare MINIMUM time between readings. Some people recover faster than others...

    Even doctors arent consistant. fro

  • by Anonymous Coward

    Human blood pressure should be measured in centimeters of mercury, not millimeters. Saying a patient's blood pressure is say 135/78 is misleading, since blood pressure is DYNAMIC and continuously changes MOMENT TO MOMENT. Whoever decided it should be measured this way had either very limited knowledge of basic human physiology or a grave misunderstanding of how significant figures work.

    When you have an event like a concert, people say "28,000 people attended" or whatever. They don't generally claim 28,351

    • by Anonymous Coward

      Oops. /. fucked up my less-than and less than or equal to symbols. Sorry about that. But you understand what I'm getting at, right?

  • My doctor got a 170/90 off me from their machine. When tested with a trained nurse and a spigometer, I was 124/80.

    I've never had them *underreport* but I've had them over report many times in my life.

  • Why not say 100% MAY be inaccurate. For that matter, maybe NONE are inaccurate. Maybe....
  • If the FDA is not requiring these devices to be accurate and precise then could not some private entity offer validation services of their own? I'd think a seal of approval for accuracy would be worth something for both makers and consumers, that can translate to real money.

    Think of the Underwriters Laboratory, it is a private company that tests and approves electrical devices for safety. People that try to sell something not approved by them will have problems. Stores are not likely to even put them on shelves if not UL approved.

    I've also seen a bunch of comments on how physicians and drug makers make a lot of money on blood pressure medications and so they are not really interested in an accurate blood pressure meter. I don't agree as I'd think that there is a lot of liability in prescribing medications for those that do not need it.

    Let's assume that this is true that since physicians and drug makers are set on handing out meds for money then would not market forces work in offering alternatives? Do not insurance companies play a role? It's rare for people to pay for medical care out of pocket. The insurance companies see a payout for high blood pressure as a cost. I'd think that it would be in their best interest to make sure that those that truly have high blood pressure have it treated and those that don't are not given medications that can have harmful side effects.

    I think that if this a real problem then some insurance companies should get together and make sure these meters work like they should. I would think that fixing the meters could save them a lot of money in payouts for medications and care. It would also have the side effect of a healthy public. If appealing to profit doesn't work then appealing to principles should.

  • by Anonymous Coward

    I don't know if this has anything to do with the Ars article but here's a comparison study comparing oscillometry and auscultation for BP measurements.

    https://bmccardiovascdisord.biomedcentral.com/articles/10.1186/s12872-017-0521-6

    From the conclusion, in part; "the systolic BP value measured by oscillometry may be 27 mmHg higher or 17 mmHg lower for patients with SR [sinus rhythm] and 24 mmHg higher or 12 mmHg lower above the BP values measured by auscultation for patients in AF [atrial fibrillation]. The w

  • by Antique Geekmeister ( 740220 ) on Friday June 09, 2017 @07:20PM (#54588725)

    It's less than 5% in a system that easily varies 20% in the course of an hour, and than vary nearly 50% in moments under stress. It's also easily affected by flexing the arm sitting in a different chair.

  • by Anonymous Coward

    They compared home machines with gold standard. They should have also done doctor's office machine with gold standard. Decisions based on home measurements rarely take into account 5mmHg on the other hand, at doctor's office, decisions are based on 5mmHg.

  • by Anonymous Coward

    on a 5mmHg difference in individual measurements reported by a patient. Your circadian rhythm double amplitude in sys and dia are each more than that and most people don't even factor those in.

  • by Dan East ( 318230 ) on Friday June 09, 2017 @08:03PM (#54589019) Homepage Journal

    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.

    • by i.r.id10t ( 595143 ) on Friday June 09, 2017 @08:55PM (#54589231)

      Just texted one of the nursing instructors (LPN,ASN,BSN degrees/certs) and she says the way they teach to do it is to do a quick check to get an idea as to where it will be and then sloooowly release down through to take the actual measurement, for exactly the reasons you state.

    • > When using a sphygmomanometer and auscultating for blood to begin flowing through the veins... Don't you mean auscultation of the brachial artery? I don't think you'll hear any Korotkoff sounds from the veins. I agree with you about slowly releasing the cuff while listening for that first sound to get an accurate systolic pressure.
    • My impression from reading about blood pressure measurement is that the actual value, not just its uncertainty, also depends on the rate of release. The rate of release is supposed to be part of the measurement standard. This is one of the biggest reasons that the manual method is very uncertain, it is hard for a human to do it with a constant, fixed release rate. If you "slow down" near the expected pressure like some suggest --- I think you're doing it wrong. Also, as others have said, a single BP mea
  • by Anonymous Coward

    There has been a lot of news about scientific articles being bunk.
    Is this a good, de-bunking article, or a bad article with questionable science?

    They did not publish their raw results, only statistics for strange combinations of the data.
    They did say they excluded one patient because the reference measurements were not consistent between two observers.
    That seems like bias against the automatic measurements.

    I think from the data they published, it's impossible to tell if the article is fud or good informatio

  • by thegarbz ( 1787294 ) on Saturday June 10, 2017 @05:55AM (#54590635)

    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.

    • 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

      Good list. Sadly, most people are completely unaware of the things you outlined. They measure their BP once and think that's all there is to it. No doctor will use a single measurement to make any treatment decision.

    • Yep, I would say this is likely another case of reporting doing more damage than good. People are going to react by not trusting the blood pressure monitor without understanding that it was never supposed to be that accurate in the first place. At what point is it just unethical to go for the scare headline at the cost of putting people's health in danger.
  • Has anyone actually read the AJH article in question:

    "In summary, although the mean BP differences between home BP monitors and auscultation were within 5 mm Hg, over two-thirds of devices tested exhibited a systolic or diastolic BP difference of 5 mm Hg, a degree of BP difference considered to be clinically important."

    So, in average most of the tested BP monitors were off by less than 5 m Hg.

    Nuff said ...

  • I take my BP meter into the doctor's office, I let them measure my BP with their gear and then I use mine to take a reading for comparison. The readings are (usually) very close.

    Note that your BP can vary considerably over the course of just a few minutes depending on your environment and how you're reacting to it. Stress, eating, movement, etc can make the results vary significantly.

    Never use any single BP reading as an "accurate" measurement. You normally need multiple readings over an extended period of

  • 5 or 10 points ain't nothing. You've clearly never had high blood pressure issues.

    This "ballpark figure" for home use is about knowing when you should contact your doctor because something is well wrong (20, 30, 50 points or more) out of your normal range. Yes, really shitty ones should be banned, but doctors measure their own at the office professionally for clinical decisions.

    I've had doctors come in and personally do my high blood pressure multiple times themselves because the nurse's measurements seem

  • I have a few things to say about this and I hope you'll bear with me. This is an issue of importance to me and although I'm not a physician or clinician I have some background and have done a great deal of research on the issue in part because I've developed a free (with no advertisements!) mobile/desktop web-app to try to help people take control of, manage, track and report their BP over time. The app works well and I'm about to roll it out for general use (just testing with friends for now). But to the a

I go on working for the same reason a hen goes on laying eggs. -- H.L. Mencken

Working...