Libre Vs Finger Prick
- Thread starter nyad21
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Excellent video. It is interesting that the people at Libre do not seem to want to discuss this.
Does this explain the "15 minute delay" which is discussed here? That may explain why in my readings that the two values are exactly the same. It may be that the trend arrow was horizontal for the 15 minutes while blood glucose had not changed.
I had another set of measurements this morning where the Libre sensor and the Libre test strip were exactly the same. My Breeze2 test strip differed by only 7% which is acceptable.
Does this explain the "15 minute delay" which is discussed here? That may explain why in my readings that the two values are exactly the same. It may be that the trend arrow was horizontal for the 15 minutes while blood glucose had not changed.
I had another set of measurements this morning where the Libre sensor and the Libre test strip were exactly the same. My Breeze2 test strip differed by only 7% which is acceptable.
I find there is inconsistency between Libre and finger prick. Last 3 months I only relied on Libre and found that my reading had gone from 51 to 54. I have now decided to use both and hopefully have a better control
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They were pretty upfront about the 15 minute delay whenever I spoke to them, and yes it does explain the 15 minute delay.
I find the Libre folk unwilling to discuss the fact that some people get completely erroneous results.... Though to be fair, they gave me several free sensors and a new reader when I was trying to get the system to work for me.
I don't trust uncalibrated Libre sensors!
I only use the LibreLink app to activate new sensors, then I use xDrip+ for my readings as it forces you to calibrate the Libre sensor when assigning a new one. xDrip+ always matches my blood tests within 0.1 mmol, whereas LibreLink never matches and can be up to 3.5 mmol out. If you've an Android phone try xDrip+, it'll make a world of difference to your sensors accuracy.
I always do a finger prick in the morning to use as a calibration test. I find the sensor is quite often out on days 1 or 2 and the last day.
Paul, quick question, if I may - I've been using xDrip+ for about a year now with libre and a blucon transmitter. Agree totally with what you say about calibration tightening it up, but can I ask, are you using it with a transmitter, or just using the nfc scan function without a transmitter?
I'm still using a September 17 version of xdrip+ (haven't been updating as it's working and don't want to risk breaking it with updates!) and that version is littered with warnings that the nfc scan function was experimental and might break sensors so proceed with caution - see screenshot.
I'm curious to know if they have improved in later versions the scanning feature so that it's no longer got the use at own risk warnings?
If so, that whole calibration option it opens could be really useful for people who want to tighten up libre without committing to a transmitter.
What is this xDrip+? I tried to search for it but everywhere I look, all I get is why to use it, benefits of it, it's history, and software packages to download. Still I have no idea what it is.....
Also, you mention that one can calibrate the Libre system. Exploring the settings, I see that a test solution is used. How does one obtain said solution?
After all my discussion with Libre about accuracy problems, they never mentioned this. How bizarre is that?
P.S.
Too bad there is no pixel size smaller than 1 so that these web designers could then guarantee that the text boxes would be totally invisible.
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It's an android app which receives data from a variety of cgm transmitters and displays it as a graph on the phone.
With libre, we can buy third party transmitters from companies like www.ambrosiasys.com and www.miaomiao.cool (one-off cost ranges between £100 to £150, miaomiao is about 150), attach them to our libre sensors, the xdrip+ app will tell the transmitter to read the sensor every 5 minutes, the app then shows the readings on a graph. See pic below for what it looks like.
The reason many of us like it is that, for that initial outlay of about 100 - 150 quid for the transmitter, it turns libre into full on cgm: hypo/hyper alerts, predictive simulations, iob counter.
And being able to calibrate: I wake in the morning, the glucose in my blood is likely to be similar to glucose in my interstitial fluid which is where libre is measuring.
So I do a bg test, let's say it's 5.6. I go to the Add Calibration page in xdrip+ and tell it that number.
Meanwhile, the sensor filament is sitting there measuring glucose in interstitial fluid and sending a raw number to xdrip+ to interpret as a bg level.
If I've told xdrip+ that the raw number which the sensor is reading and sending to it at a time of stability means 5.6 in the real world from an actual bg test, that means that xdrip+ is going to make a much better job of interpreting other numbers it gets from the sensor/transmitter.
I've calibrated xdrip+, made it more accurate, by telling it that when it gets a number from libre, it means x in the real world, not what libre calibration meant in the factory.
It's not a one-off, though. Calibration/sensors wander, so I might do it a couple of times a day.
Those are two separate things. Remember that the libre reader does two separate things: it can scan the sensor, but can also be used as a normal bg meter (and here's a third, ketone meter).
Calibration is to do with using the transmitters which I've mentioned above.
The control solution tests you mention is just used in relation to checking how it's working as a bg meter. Control solution tests don't have anything to do with sensor scans.
It's a brave new world with these here gadgets, Gork, takes a bit of time to get used to their quirks, but it's worth it in the end!
Here's the xdrip graph to give an idea of what it looks like - the blue dots are real life 5 min inputs from libre and the transmitter, the purple dots are a simulation of where I might be going, the green lines are suggestions of how much iob I've got:
Apparently Libre requires the "control solution" to calibrate. I wonder where I can get that and why Libre did to send some with the meter.
150 quid ($200) for a blue tooth transmitter. Interesting. I doubt I will spring for one. The pic looks good though.
I wondering how much of that information is actually useful rather than thoughtful to look at.
150 quid ($200) for a blue tooth transmitter. Interesting. I doubt I will spring for one. The pic looks good though.
I wondering how much of that information is actually useful rather than thoughtful to look at.
For a T1, it is stunningly useful. Compared to strips alone, any sort of cgm is life changing. It allows us to respond in real time to developing situations before they become bad.
This stuff means that, instead of dealing with hypos and hypers after they have happened, situations which often require a sledgehammer to deal with, and can have messy consequences, I can see highs and lows starting to develop, and take small subtle steps to deal with them in advance before they get anywhere near a messy zone.
Understood. I do not know much about T1. As T2, I really have only the low reading as a short-term/immediate problem. I can see how immediate status is valuable for those T1. I was not looking at the chart that way.
No probs, Gork! It's a learning experience for all of us - I didn't know much about T2 before I started looking around here.
Hi i am T 1 for 5 years 7 months . This is my 2nd freestyle and I think it's great I was pricking my fingers 8 10 times a day I have only checked it twice and been slight difference I could not get reader so I had to get I Phone 7 hope I can keep up the expense as you do not get it on NHS in perth shire. Good luck all
I suppose the sentence you have written -The Libre uses a different mechanism to calculate BG - for a start, it doesn't use blood; it uses interstitial fluid. - it doesn’t calculate BG at all it is the glucose levels in interstitial fluid
How do you know what is accurate? How did you test the accuracy of the meter used?
Blood glucose levels are different around your body as is interstitial fluid. There is no direct correlation between them
There is an algorithm which is used to approximate the BG from interstitial fluids. I have no ideas how it works (but Google probably has some theories). The Libre sensor/reader does the necessary calculations.
As many have said, this can work out quite accurate ... but not for everyone or every time. I understand it struggles when BG is changing quickly such as during exercise.
There's a paper at the link below describing the relationship between blood and interstitial fluid in a cgm context.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2903977/
Most of it is way too sciency for me to understand but I found it quite helpful when I first started using cgm to get a broad idea of when and why there might be differences.
As many authors have said, notably William Lee Dubois, one of the tricks to using cgm well is knowing when it's likely to be right, but just as importantly, when it's likely to be wrong. Understanding the relationship between bg and ifg is key to that.
Long term users all know that there are times when we can place a fair bit of reliance on what the cgm is telling us, for example, when it has recently been calibrated in a relatively stable resting state, and will happily bolus from it, but there are other times when we will look askance at it and cross-check against a strip test. The knack is being able to tell which is which and just really comes from regular use of it in real life.
It's swings and roundabouts, but it's the best we've got with current technology, and I would be reluctant to no longer have it.
