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Freestyle Libre Sensor: highly inaccurate??

Discussion in 'Blood Glucose Monitoring' started by TedTomato, Mar 4, 2018.

  1. Zilsniggy

    Zilsniggy Type 2 · Well-Known Member

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    Sorry, I see as I find....I disliked Abbot's customer service, they refused to replace the machine, or offer a refund, denied any fault in it without examining it, not great. But we are all different, as you say, and all appear to have differing experiences. I'm different from you in that I have an opposing opinion based upon my experience of the Freestyle, and Abbot's poor customer service. Should I change that because someone else had a different experience?
    And no, I won't be buying any more of an item that is completely useless to me. I do still think that those users who continue to have success are in the minority, and that the machine isn't comp[letely ready for the market.
    I can agree to differ if you can;)
     
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  2. johnBigBad

    johnBigBad Type 2 · Newbie

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    Glucose-readings-bias.png I have found problems on only 1 of my last 13 sensors...apart from the few I have knocked off my arm.

    I now tape over the sides of my sensors and have almost had perfect working for 14 days with this extra tape.

    For those who doubt the accuracy, as per Abbotts' suggestions, a series (they suggest 5 minute apart) simultaneous sensor vs finger prick tests work, and backup the finger prick tests with another manufacturer's blood test. I have found Optium tests strips are usually within 6% of Performa test strips.

    Loading the results to PC and using the Freestyle Libre software shows the bad sensor bias very quickly and easily (compare the dots above the sensor line values - all high).

    This image was enough for Abbott to replace this sensor.
     
  3. TedTomato

    TedTomato Prediabetes · Active Member

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    My first sensor was providing readings all over the place, in term of values and also trends.

    I emailed Abbot but they never replied.

    I then called, and spoke to someone fairly quickly. A set of three readings between the Libre and a blood tester was enough to show that the difference was more than 15% each time. He confirmed that a replacement would be sent, and it arrived the next day (so they do keep stock available for replacements), along with a return envelop for the faulty one.
     
  4. TedTomato

    TedTomato Prediabetes · Active Member

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    My point was that those devices are advertised to measure glucose levels, not some other unit.

    Yes, I have also considered the delay between a blood test, and the Libre reading, which could be 15-20 minutes behind, but that didn't make much difference most of the time, in term of understanding the large differences.

    My conclusion is currently:

    • A large proportion of Libre sensors are faulty, and that proportion seems to be too high for something marketed (not just in trials), expensive and even funded by the NHS in some cases. Abbot seems to know that some batches are faulty, were damaged during transport etc., but those are still sold
    • Some people will have their body rejecting the device/filament, meaning inaccurate readings for several days and/or first sensor being used. It seems to be known, but Abbot doesn't specifically advise to position the sensor and wait 24 hours for activation
    • I don't understand why calibration is not possible on the app, to readjust readings based on occasional blood tests
    • Device is more about trends (go up or down based on specific food for instance)/long term trends (weeks), as opposed to actual values
    • I don't understand either why memory is limited to just 8 hours. Surely, the memory chip could keep something for longer (e.g. 12 hours)
    • It's very interesting and promising technology, but still early days and therefore hit and miss. I am sure Abbot and others must be working on a better version, with more memory, Bluetooth etc.
     
  5. EllieM

    EllieM Type 1 · Moderator
    Staff Member

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    This is the one I really wish for, but I think they wanted to go for extreme ease of use and no manual calibration, reckoning the positives (promise of no more fingerpricks) outweigh the negatives (a small number of people whose bodies just don't work well with the sensor). As one of those small number of people I regret this, but guess I should investigate the dexcom.
     
  6. TedTomato

    TedTomato Prediabetes · Active Member

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    My second sensor has expired today, after 14 days.

    Last measurement provided was 4.9 while my blood tester gave 6.3.

    First sensor was all over the place, always reporting much higher levels.

    This second sensor has been consistently reporting lower numbers, by at least 1mmol/L.

    Looks like I am getting readings with 30% tolerance at best...

    At least, the second sensor seemed to report trends properly, but actual values were very often wrong.
     
  7. DunePlodder

    DunePlodder Type 1 · Well-Known Member

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    On those figures, if the "true" value is actually mid way i.e. 5.6, then both the CGM & the Libre are within the claimed 15% tolerance.
    You seem to assume that your blood tester is perfect.
    Just playing Devil's Advocate, I know it can be frustrating.

    If you were to use xDrip+ with the Libre then you could calibrate the readings - this would get over a consistently lower reading.
     
  8. bravopapa

    bravopapa Type 1 · Member

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    Please help anxious dad and just picking up on this forum. We have a beautiful 8 year old daughter sadly diagnosed T1 (although possible MODY but that's another story) 3 weeks ago. She has been more upset by finger pricks than insulin shots (Basel Bolus 4 per day). We convinced her that Libre would reduce frequency to only pre-meal/insulin calculation and hypo treatment. So excited at prospect we invested in Libre (plus butterfly shaped rocktape stickers etc that an 8 year old NEEDS!).

    Applied nearly 36 hours ago and our reading are crazy. She is still running high as then slowly bring down the carb ratios in the meter but we have just finger pricked a 9 and the Libre is showing 15.8. In fact, the last 3 readings we have pricked against have shown a 3,5 and now 6 mmol difference. I accept they "calm down" but this is just infuriating, especially after the fear and tears we had applying it. I am really not amused or impressed. Due lunch bolus in 25 minutes so will compare the two again and report back, Anyone had such variation during the first 48 hours. I must add that the first one we did had a variation of just 0.2mmol at 2 hours activation???

    Anxious Dad.
     
  9. kev-w

    kev-w Type 1 · Well-Known Member

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    Can I ask which finger pricker you use? Just there's good and bad ones, in my opinion the Accucheck Fast Clix is the softest and doesn't need 'priming' with the click announcing the sharp pain to come, that could help with the finger pricks.
    I'm new to the Libre and haven't had any problems, but can see odd readings when my bloods see saw and I check with a stick but would suggest you contact their customer services, somewhere in this thread I think there's a post describing what they need you to tell them to obtain a replacement.

    Has your local CCG commissioned the device as it is just wrong that young kids are being denied access to it and I'd be pestering the clinic on a regular basis for a prescription.
     
  10. therower

    therower Type 1 · Well-Known Member

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    @bravopapa . Have you researched the Genteel lancet , it gets some good reviews especially for youngsters.
    As good as the libre is it doesn't suit all. Maybe consider using a CGM.
     
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  11. bravopapa

    bravopapa Type 1 · Member

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    Thank you for the prompt replies. We do currently use a fastclix with an Aviva Expert. I preferred the old multiclix as find that for an 8 year old the force required for the fastclix can make it difficult. I will certainly take a look at the Genteel, thankyou.

    We just took a lunch reading and the Libre was showing 14.8 and BG from Aviva Expert was 12.9. So better than before. Maybe it is just out at the upper and the lower end of a blood range and we are running very high at the moment.

    Id like to believe that even if it is 2-4mmol out it is still accurate in "trend". I will leave it alone and talk with Abbott on Monday when the CS team are open. Time to tell daughter she is back to extra finger pricks as well as Libre in the arm. Might need a shopping trip!!!!
     
  12. TedTomato

    TedTomato Prediabetes · Active Member

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    It's more like testerS... I have checked several times against various blood testers. They all agreed with their readings within maybe 0.3 mmol/L, while the Libre was 1.5 above or below.

    I am done with the Libre, and will wait for a new version or competitor ones.
     
  13. urbanracer

    urbanracer Type 1 · Expert
    Retired Moderator

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    This is more about reliability than an accuracy issue but after a painful sensor application, I withdrew the applicator to find that the filament protective sheath had detached itself from the applicator and was stuck in my arm.

    upload_2018-3-25_8-50-54.png

    I pulled the sheath out but after 4 attempts to start the sensor I took it off to find a fair bit of fresh blood under the sensor.

    Watch out for this, it hurts!
     
    • Useful Useful x 1
  14. bravopapa

    bravopapa Type 1 · Member

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    so BG from Aviva Expert was just 8.2 and Libre is reading 12.9. I am really not impressed after 3 days of increased not decreased stress/anxiety caused by this product. Might just get a full refund and go Dexcom. We only chose Libre for size as it is for an 8 year old. But with Dexcom having calibration and our daughter having to prick for bolus anyway, it may work better.
     
  15. bravopapa

    bravopapa Type 1 · Member

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    My Daughter swims a lot so I used SkinTac and Rocktape. Guess I am going to be in the bad books when I try to take this off.
     
  16. PW1

    PW1 Prediabetes · Well-Known Member

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    Just adding my experience to this discussion on the Libre. One thing I have noticed with Freestyle Libre, is that sometimes, when I am having to work on keeping the carbs low, or when I’ve eaten way too many carbs, there seems to be a noticeable difference between the blood sugar and the interstitial sugar.

    My guess for these times is that my body is doing something sensible - like trying to maintain a steady blood sugar by pushing surplus glucose to the muscles, where it can be used up. This guess is based on the experience that I see in my glucose results. It happens more often when I am low carb than it does when I’ve been off low carb for a week or more. It is particularly noticeable when I am actively working to reduce the carbs and my body is adjusting to a change in carb values.

    I have also found, that for me, when the way of eating falls apart the arm-based Libre sensor often reads higher peaks than blood testing. Again, I’m guessing this might be because my body is pushing the glucose to somewhere that it can be used instead of letting sit in the blood. Especially since things seem to settle when my macronutrients are more stable.

    I am however pre-diabetic with reactive hypoglyceamia, so injections and medication do not come into my calculations - just carbs, protein and fat. I use the Libre to help me stay aware and not hide from the pre-diabetes. And to help me know when the meals are working - that and a clearer head with more energy, keep convincing me that keto works for the way my broken body uses energy. It is taking so long to get the way of eating right and to find the meals that I can manage in different situations. Low carb was first suggested to me 10 years ago for a different energy related condition, I’m still struggling to stay on track, but it really does help my body and brain.
     
  17. Scott-C

    Scott-C Type 1 · Well-Known Member

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    I wonder whether the recent supply difficulties have led to them letting production/calibration standards slip?
     
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  18. bravopapa

    bravopapa Type 1 · Member

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    Scott-C. I had thought the same. I will speak with Abbott CS tomorrow and report back here. I don't know what I would find acceptable? maybe no more than 1 mmol in either direction. Anyone else dumped Libre and gone Dexcom? anyone had terrible accuracy (More than 4mmol out) on Dexcom?
     
  19. TedTomato

    TedTomato Prediabetes · Active Member

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    CS will see if it's 15% above or lower than measurements taken with a blood tester.
     
  20. bravopapa

    bravopapa Type 1 · Member

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    Thanks TedTomato - Looking at the figures over the last few days it is consistently reading higher than Aviva Expert by 25%-45%. Now I have actually calculated the difference I am even more shock, this sensor must be way off. Other than size and applicator "friendliness" what disadvantage is any does the Dexcom have and why did those of you using these as adults chose the Lbre? Just looking for some decision validation.
     
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