SamElliott1997
Well-Known Member
Constantly at least 15% higher than actual blood glucose measured using 2 different meters that are with each other.
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FREESTYLE LIBRE ON SALE!!!!
- Thread starter Emmotha
- Start Date
Constantly at least 15% higher than actual blood glucose measured using 2 different meters that are with each other.
dbr10
Well-Known Member
I do wonder about the accuracy of these sensors compared with a meter
I have only been on the Freestyle for 7 weeks and absolutely love it. I feel it gives lower readings than on my glucometer but each glucometer gives a slightly different reading anyway. I have 2 different ones and have now decided to trust the Freesyle and go from there.
Florence5
Florence5
NikiMilligan
Active Member
Bought 3 Libres at the end of August (can’t afford to use all the time) 1 to use immediately, one in case I got a chest infection and needed steroids, and one for general educational purposes.
Just gone to put on the second one, only to discover it expired in October.
Gutted! Not least, because it means I can never have an emergency one in stock again for my asthma management, not with a 2 month expiry.
Oh well, there a hundred quid I won’t see again!
Just gone to put on the second one, only to discover it expired in October.
Gutted! Not least, because it means I can never have an emergency one in stock again for my asthma management, not with a 2 month expiry.
Oh well, there a hundred quid I won’t see again!
slip
Well-Known Member
An out of date sensor will still work, it's accuracy might be a bit suspect - but then again it might be perfectly spot on.
Abbott did go through a spell of having short expiry dates - mainly due to stock level issues, but that appears to be fixed now and expiry dates are pretty much 6 months at least now.
It takes a while to get used to the idea that there are TWO time difference factors at work between BG and Libre. Firstly interstitial BG lags 10 to 15 mins behind BG, and secondly Libre only samples every 10 mins. When hypo or heading towards hypo it is advisable therefore to measure by finger prick for immediate results. Generally however I find good agreement between BG and Libre except when hypo or the trend arrow is vertical up or down and changes are too fast for Libre to reflect. Once you get to grips with that Libre is a great help. It has helped me reduce my HbA1c very substantially over the last year or so probably halving my risk of major complications.
Just got my Libre yesterday, and I am blown away so far... Expected a stab of pain applying the sensor - but it was absolutely painfree!
After 21 years of T1 Diabetes, doing exactly the same thing (short acting, long acting, finger pricks) this feels like a game changer! If my wife suspects I'm going hypo in the night now, she can just scan me
Loving it.
Abbott can clean up with this device. I'll have to self-fund mine, but it is a no-brainer so far. I'll find the money.
I hope and pray, that Abbott reduce the price of the sensors in the future. In any normal market, prices drop once development and setup costs are recouped. With big pharma (diabetes in particular), I'm not convinced. Let's hope other companies are encouraged by Libre's success to up their game and come out with competitor products that will get the prices trending downwards.
After 21 years of T1 Diabetes, doing exactly the same thing (short acting, long acting, finger pricks) this feels like a game changer! If my wife suspects I'm going hypo in the night now, she can just scan me
Loving it.Abbott can clean up with this device. I'll have to self-fund mine, but it is a no-brainer so far. I'll find the money.
I hope and pray, that Abbott reduce the price of the sensors in the future. In any normal market, prices drop once development and setup costs are recouped. With big pharma (diabetes in particular), I'm not convinced. Let's hope other companies are encouraged by Libre's success to up their game and come out with competitor products that will get the prices trending downwards.
Celsus
Well-Known Member
There is typically a 12+ months expiry horizon on the Libre sensors that I get.
So stocking up for 4-6 months of supplies of them when going shopping.
If you observe a shortdated one with e.g. max 3 months remaining then demand to get one with longer time left instead.
Celsus
Well-Known Member
Hi @ECDRUM , just to clarify a few points in your technical description of the libre sensor above. (and I don't work for or have commercial interests in Abbott) The Libre sensor was initially programmed by Abbott to make a bg reading that is being stored in its memory for every 15 minutes in the beginning. So if you dont swipe the sensor with your bg meter, then the sensor will by itself read and store the bg value for every 15 minutes. I have not seen any documentation for that this has been changed down to 10 minutes. If it is has, OK great, but it wont change much though we of course do agree its better with more granularity.
The thing is however that when you force a swipe with your bg meter over the sensor, then you also force an instant read from the sensor which it therefore stores and uses this latest read to calculate the most viable bg level you have at present. You will also recognize that this is correct on how it works if you ever tried a rapid drop/rise in bg, as it doesn't take 10 minutes before you see the values on your meter changes when swiping the scanner. They change by the minute, which is also the shortest timeframe the sensor and meter is able/willing to take a new sample data point for its algorithm to use.
So why your need to fingerprick as you state above? (or certainly not for the reasons stated)
If you see a vertical drop indicator on your sensor when below 4 or if you see a meter reading below 3.5 or further down is really irrelevant. You need sugar in any case as finger pricking wont change that.
extraspike
Newbie
I have had ordering an delivery issue with sensors from AccuLibre...they cannmot confirm orders and seem to have real issues with their supply chain. I hope that they are not victims of their own success. I have using the AccuLibre CGM system for 18 months now and have really come to rely on it quite heavily. I think that the really need to support their committed long term customers otherwise we will need to look to go elsewhere.
Does anyone have experience of using more than one CGM system?
David
Does anyone have experience of using more than one CGM system?
David
Hi @ECDRUM , just to clarify a few points in your technical description of the libre sensor above. (and I don't work for or have commercial interests in Abbott) The Libre sensor was initially programmed by Abbott to make a bg reading that is being stored in its memory for every 15 minutes in the beginning. So if you dont swipe the sensor with your bg meter, then the sensor will by itself read and store the bg value for every 15 minutes. I have not seen any documentation for that this has been changed down to 10 minutes. If it is has, OK great, but it wont change much though we of course do agree its better with more granularity.
The thing is however that when you force a swipe with your bg meter over the sensor, then you also force an instant read from the sensor which it therefore stores and uses this latest read to calculate the most viable bg level you have at present. You will also recognize that this is correct on how it works if you ever tried a rapid drop/rise in bg, as it doesn't take 10 minutes before you see the values on your meter changes when swiping the scanner. They change by the minute, which is also the shortest timeframe the sensor and meter is able/willing to take a new sample data point for its algorithm to use.
So why your need to fingerprick as you state above? (or certainly not for the reasons stated)
If you see a vertical drop indicator on your sensor when below 4 or if you see a meter reading below 3.5 or further down is really irrelevant. You need sugar in any case as finger pricking wont change that.
Hi Celsius
Of course a finger prick will not change your BG but it will tell you what your BG is at that time as opposed to what your interstitial is at that time (or when the sensor last sampled). In normal circumstances the difference is minor and of little importance but when hypo or when BG or interstitial is changing rapidly the 10 or 15 mins difference could be material. That is why Abbott recommend a finger prick when Libre readings are low or changing rapidly.
Celsus
Well-Known Member
OK, but still don't see why that would change your course of action to correct?
e.g. You Libre meter says "LO". What should your bg meter say for you to decide not to take any sugar?
Or you Libre meter says 3.5 with a vertical drop arrow presented. What should you meter say for you to decide not to take any sugar?
I am of course only posing these questions under the condition that the Libre measures are accurate.
In both cases your classic old finger prick meter would also say your bg is below 3.8mmol/L.
Personally I would take some sugar in both cases. And it does not matter if the reading result is instant or what your bg was 6 minutes ago. Its limited how much your bg drop or climb in 6 minutes time. Abd personally, what really makes the big ad better difference between the two measurement types is that you see the trend and speed of that trend on the Libre. As that tells you then if your drop is brutal and you better go big on your glucose intake. Or e.g. yes you are low but your trend is anyway on the way up, so maybe you don't even need anything or you can go gentle just with a small amount of glucose to get above e.g. 4mmol/L. Your fingerprick does none of that and if only having that single instant measure, you typically overreact either one way or the other. All of course except if you keep taking a new finger prick test for every 1 minute the next 10 minutes or so. (some might do so out there?!
)Yes, I know we have heard of some individuals where when they have tried a Libre where they don't appear to get reliable results. But that is definitely not the norm, as the Libre would then never have been given approval to market. Personally I would also have loved to see either Abbott or these individuals really trying to find the root cause for such wrong readings, but guess we have to be patient as none seem to be willing/able to go that extra mile. Actually understand Abbott would be welcoming them with open arms in the area where I live, but so far no takers. We have also seen how the Libre system has gone through with flying colors in being consistent and reliable when in clinical studies with larger population bases. Reason also why they can write the following:
---
Is FreeStyle Libre accurate?
The FreeStyle Libre system is clinically proven to be accurate, stable and consistent over 14 days compared to blood glucose testing without the need for finger prick calibration.
- In a clinical study, the FreeStyle Libre system achieved 11.4% Mean Absolute Relative Difference (MARD) compared to blood glucose testing.
- 99.7% of glucose results fall within Zone A and Zone B of the Consensus Error Grid.
Interstitial fluid-based glucose readings are a reliable indicator of blood glucose levels.
The physiological lag in ISF glucose, with respect to changes in blood glucose, is about 5-10 minutes.
- The average lag time of the FreeStyle Libre system is approximately 5 minutes, which is unlikely to impact routine day-to-day treatment decisions.
While referring to a couple of clinical studies:
Parkes J, Slatin S, Pardo S, et al. A new consensus error grid to evaluate the clinical significance of inaccuracies in the measurement of blood glucose. Diabetes Care. 2000;23(8):1143-1148.
Rebrin K, Sheppard NF Jr, Steil GM. Use of subcutaneous interstitial fluid glucose to estimate blood glucose: revisiting delay and sensor offset. J Diabetes Sci Technol. 2010;4(5):1087-1098.
There are several other studies performed using up to date methodologies, (cbg measures obtained by using the needle type of sensors which is the type used by Libre and a few others) when measuring the interstitial fluid glucose values. Where they typically come to a delay of max 6-8 mins.
But @ECDRUM I like your questioning around this subject. And one thing I also haven't given so much thought about myself previously is at the root of what we discuss here:
If your bg is at e.g. 6mmol/L and you take your bolus for a meal. And then you don't eat anything. What is then the fastest bg mmol/L /10 minutes drop that you will be able to measure as result of that?
Kids, don't try this at home.
But maybe a couple of us more experienced hypo-maniacs could try and check it out when sitting at home on the sofa doing nothing else next weekend?
And what should then be the criteria for that we condemn the Libre to fail this test?
E.g. if my Libre tells me 5mmol/L and have a vertical drop arrow listed, I would still save it in time most cases I believe. But it takes of course that it doesnt drop e.g. 2mmol/L over 10 minutes, as in that case I would not be able to save it without going hypo. So question remain, how quick would the bg need to drop over 10 minutes for the Libre not be good enough? And how quick would the Libre indicator arrow then start to pick it up anyway?
OK, but still don't see why that would change your course of action to correct?
e.g. You Libre meter says "LO". What should your bg meter say for you to decide not to take any sugar?
Or you Libre meter says 3.5 with a vertical drop arrow presented. What should you meter say for you to decide not to take any sugar?
I am of course only posing these questions under the condition that the Libre measures are accurate.
In both cases your classic old finger prick meter would also say your bg is below 3.8mmol/L.
Personally I would take some sugar in both cases. And it does not matter if the reading result is instant or what your bg was 6 minutes ago. Its limited how much your bg drop or climb in 6 minutes time. Abd personally, what really makes the big ad better difference between the two measurement types is that you see the trend and speed of that trend on the Libre. As that tells you then if your drop is brutal and you better go big on your glucose intake. Or e.g. yes you are low but your trend is anyway on the way up, so maybe you don't even need anything or you can go gentle just with a small amount of glucose to get above e.g. 4mmol/L. Your fingerprick does none of that and if only having that single instant measure, you typically overreact either one way or the other. All of course except if you keep taking a new finger prick test for every 1 minute the next 10 minutes or so. (some might do so out there?!
Yes, I know we have heard of some individuals where when they have tried a Libre where they don't appear to get reliable results. But that is definitely not the norm, as the Libre would then never have been given approval to market. Personally I would also have loved to see either Abbott or these individuals really trying to find the root cause for such wrong readings, but guess we have to be patient as none seem to be willing/able to go that extra mile. Actually understand Abbott would be welcoming them with open arms in the area where I live, but so far no takers. We have also seen how the Libre system has gone through with flying colors in being consistent and reliable when in clinical studies with larger population bases. Reason also why they can write the following:
---
Is FreeStyle Libre accurate?
The FreeStyle Libre system is clinically proven to be accurate, stable and consistent over 14 days compared to blood glucose testing without the need for finger prick calibration.
9. Is interstitial fluid an adequate replacement to blood glucose testing?
- In a clinical study, the FreeStyle Libre system achieved 11.4% Mean Absolute Relative Difference (MARD) compared to blood glucose testing.
- 99.7% of glucose results fall within Zone A and Zone B of the Consensus Error Grid.
Interstitial fluid-based glucose readings are a reliable indicator of blood glucose levels.
The physiological lag in ISF glucose, with respect to changes in blood glucose, is about 5-10 minutes.
---
- The average lag time of the FreeStyle Libre system is approximately 5 minutes, which is unlikely to impact routine day-to-day treatment decisions.
While referring to a couple of clinical studies:
Parkes J, Slatin S, Pardo S, et al. A new consensus error grid to evaluate the clinical significance of inaccuracies in the measurement of blood glucose. Diabetes Care. 2000;23(8):1143-1148.
Rebrin K, Sheppard NF Jr, Steil GM. Use of subcutaneous interstitial fluid glucose to estimate blood glucose: revisiting delay and sensor offset. J Diabetes Sci Technol. 2010;4(5):1087-1098.
There are several other studies performed using up to date methodologies, (cbg measures obtained by using the needle type of sensors which is the type used by Libre and a few others) when measuring the interstitial fluid glucose values. Where they typically come to a delay of max 6-8 mins.
But @ECDRUM I like your questioning around this subject. And one thing I also haven't given so much thought about myself previously is at the root of what we discuss here:
If your bg is at e.g. 6mmol/L and you take your bolus for a meal. And then you don't eat anything. What is then the fastest bg mmol/L /10 minutes drop that you will be able to measure as result of that?
Kids, don't try this at home.
But maybe a couple of us more experienced hypo-maniacs could try and check it out when sitting at home on the sofa doing nothing else next weekend?
And what should then be the criteria for that we condemn the Libre to fail this test?
E.g. if my Libre tells me 5mmol/L and have a vertical drop arrow listed, I would still save it in time most cases I believe. But it takes of course that it doesnt drop e.g. 2mmol/L over 10 minutes, as in that case I would not be able to save it without going hypo. So question remain, how quick would the bg need to drop over 10 minutes for the Libre not be good enough? And how quick would the Libre indicator arrow then start to pick it up anyway?
For the avoidance of doubt I do believe Libre is accurate and in general I find pretty good agreement between finger prick and Libre readings. The only exception that I find is where I have been low to the extent of a LO reading on Libre and take corrective action it can take up to an hour for Libre to reflect the rising BG whereas finger prick shows rising BG within 15 mins or so. If I were to rely purely on Libre I would be likely to over correct and an hour or so later I would be reading 12 or higher. My original point was that once you are aware of the time lag this can be avoided and if necessary a finger prick test 15 mins after corrective carbs will show BG rising and give the confidence required to avoid over correction. It works for me - but each to their own.
Having self funded Libre for over a year I would not be without it as it has dramatically improved my HbA1c - but there are circumstances where an immediate BG reading is useful.
Celsus
Well-Known Member
Just checked the technical specifications behind the trend indicator arrow on the Libre Meter:
Straight arrow: BG is changing slowly
(less than 0.06 mmol/L per minute)
Arrow going down: BG is falling
(between 0.06 and 0.1 mmol/L per minute)
Arrow vertical down: BG is falling quickly
(more than 0.1 mmol/L per minute)
So for me not to catch a severe hypo coming along in time would take a very severe fast drop in bg per 10 minutes.
I will try in the weekend to measure what the fastest drop I will experience is over a 10min period after taking my highest dose which is a 5 units bolus at breakfast. Per my own ratios it should equal a 15mmol/L drop in total, but that is typically stretched out over a 1.5-2.0 hour period for the bolus effect curve, so don't expect to observe an unmanageable drop over any 10 minutes period of time during that period.
Straight arrow: BG is changing slowly
(less than 0.06 mmol/L per minute)
Arrow going down: BG is falling
(between 0.06 and 0.1 mmol/L per minute)
Arrow vertical down: BG is falling quickly
(more than 0.1 mmol/L per minute)
So for me not to catch a severe hypo coming along in time would take a very severe fast drop in bg per 10 minutes.
I will try in the weekend to measure what the fastest drop I will experience is over a 10min period after taking my highest dose which is a 5 units bolus at breakfast. Per my own ratios it should equal a 15mmol/L drop in total, but that is typically stretched out over a 1.5-2.0 hour period for the bolus effect curve, so don't expect to observe an unmanageable drop over any 10 minutes period of time during that period.
Celsus
Well-Known Member
All agreed @ECDRUM , it tends actually to be on the way up that the Libre is 'weakest'.
I often blame myself for it though, as tend to go crazy with hard carbs when having to counter a bad hypo.
But difficult really to judge as well, as the hypo in itself also makes your liver keep dumping in hours after which easily brings me into the 12-15mmmol/L range.
But like you, I was happy to self-fund it for more than 2 years until it came to my region where I live.
As it has been a complete game changer for me also.
My thoughts exactly. Strips are snaphots, cgm is the full movie, so it's so much easier to make small adjustments while still in range, instead of a big sledgehammer to sort out messes.
There's an easy way to bling it up a bit and turn it into "proper" cgm, so you'll get woken up by your phone ringing if you drop below a certain level.
www.ambrosiasys.com sell, for £96 one-off cost, a bluetooth transmitter called blucon nightrider, pic below. The founder used to work for Abbott. It's small, the same height as 2 libre sensors on top of each other, and a couple of mm wider. Not waterproof, so needs to be put on top of the sensor with an armband or sticking plaster to remove for showers, or heat seal it in a small sous-vide bag. Reads the sensor every 5 mins and bluetooths it to your phone.
Their own inhouse app, linkblucon, isn't much cop, but a free third party android app, xDrip+, initially developed for dexcom, and now capable of taking data from blucon, is a work of art. Hypo/hyper alerts, calibration, fast fall/rise alerts, bolus/insulin predictions, agp graphs, statistics, standard deviation, smartwatch integration. Lots of stuff. Pic of the graph below.
Libre is great on its own but cgm'ing it with blucon and xDrip+ takes it into a different league. The transmitter is pretty solid - had mine for almost a year now, still going fine, just need to change the cheap cr2032 battery every few weeks. There's quite a few of us using it now.
The lead developer is called jamorham, here's his main page where xdrip+ can be downloaded:
https://jamorham.github.io
Yes, I know, it a looks a bit sketchy Heath Robinson, but it works.
