CGM review: Abbott FreeStyle Libre

While working on reverse engineering glucometers I decided to give a try to a CGM solution. As far as I know the only solution available in Ireland is Dexcom. A friend of mine already has this, and I’ve seen it, but it felt a bit too bulky for my taste.

Instead, I found out on Twitter about a new solution from Abbott – the same company I wrote plenty before while reverse engineering devices – called FreeStyle Libre. When I first got to their website, though, I found out that the description videos themselves were “not available in my country”. When I went back to check on it, the whole website was not available at all, and instead redirected me to a general website telling me the device is not available in my country.

I won’t spend time here to describe how to work around the geolocking, I’m sure you can figure it out or find the instructions on other websites. Once you work around accessing the website, ordering is also limited to UK addresses for both billing and shipping — these are also fairly easy to work around, particularly when you live in Éire. I can’t blame Abbott for not selling the device in this country (they are not allowed by law) but it would be nice if they didn’t hide the whole website though!

Anyway, I have in some ways (which I won’t specify) worked around the website geolocking and order one of the starter kits back in February. The kit comes with two sensors (each valid for 14 days) and with a reader device which doubles as a normal glucometer.

The sensors come with an applicator that primes them and attaches them to the arm. The applicator is not too difficult to use even with your weak hand, which is a nice feature given that you should be alternating the arm you attach it to. Once you put the sensor on you do feel quite a bit of discomfort but you “get used to it” relatively quickly. I would suggest avoiding the outer-side of the arm though, particularly if you’re clumsy like me and tend to run into walls fairly often — I ended up discarding my second sensor after only a week because I just took it out by virtue of falling.

One of the concerns that I’ve been warned about by a friend, on CGM sensors, is that while the sensor has no problem reading for the specified amount of time, the adhesive does not last that long. This was referred to another make and model (the Dexcom G4) and does not match my experience with the Libre. It might be because the Libre has a wider adhesive surface area, or because it’s smaller and lighter, but I haven’t had much problem with it trying to come away before the 14 days, even with showers and sweat. I would still suggest keeping at hand a roll of bandage tape though, just in case.

The reader device, as I said earlier, doubles as a normal glucometer, as it accepts the usual FreeStyle testing strips, both for blood and for ketone reading, although it does not come with sample strips. I did manage to try blood readings by using one of the sample strips I had from the FreeStyle Optium but I guess I should procure a few more just for the sake of it.

The design of the reading device is inspired by the FreeStyle InsuLinx, with a standard micro-USB port for both data access and charging – I was afraid the time would come that they would put non-replaceable batteries on glucometers! – and a strip-port to be used only for testing (I tried putting the serial port cable but the reader errors out.) It comes with a colourful capacitive touch-screen, from which you can change most (But not all) settings. A couple of things, such as the patient name, can only be changed from the software (available for Windows and OSX.)

The sensor takes a measurement every 15 minutes to draw the historical graph, which is stored for up to eight hours. Plus it takes a separate, instantaneous reading when you scan it. I really wish they put a little more memory in it to keep, say, 12 hours on the device, though. Eight hours is okay during the day if you’re home, but it does mean you shouldn’t forget the device home, when you go to the office (unless you work part-time), and that you might lose some of the data from just after going to sleep if you manage to sleep more than eight hours at a time — lucky you, by the way! I can’t seem to be able to sleep more than six hours.

The scan is at least partially performed over NFC, as my phone can “see” the sensor as a tag, although it doesn’t know what to do with it, of course. I’m not sure if the whole data dumping is done over NFC, but it would make it theoretically possible to get rid of the reader in favour of just using a smartphone then… but that’s a topic for a different time.

The obvious problem with CGM solutions is their accuracy. Since they don’t actually measure blood samples (they do use a needle, but it’s a very small one) but rather interstitial fluid, it is often an open question on whether their readings can be trusted, and the suggestion is to keep measuring normal blood sugar once or twice a day. Which is part of the reason why the reader also doubles as a normal glucometer.

Your mileage here may vary widely, among other things because it varies for me as well! Indeed, I’ve had days in which the Libre sensor and the Accu-Chek Mobile matched perfectly, while the last couple of days (as I’m writing this) the Libre gave a slightly lower reading, between 1 and 2 mmol/l (yes this is the measure used in UK, Ireland and Australia) lower than the Accu-Chek blood sample reading. In the opinion of my doctor, hearing from his colleagues across the water (remember, this device is not available in my country), it is quite accurate and trustworthy. I’ll run with his opinion — particularly because while trying to cross-check different meters I have here, they all seem to have a quite wider error range you’d expect, even when working on a blood sample from the same finger (from different fingers it gets complicated even for the same reader.)

I’m not thrilled by the idea of using rechargeable batteries for a glucometer. If I need to take a measurement and my Accu-Chek Mobile doesn’t turn on, it takes me just a moment to pick up another pair of AAA from my supply and put them in — not so on a USB-charged device. But on the other hand, it does make for a relatively small size, given the amount of extra components the device need, as you can see from the picture. The battery also lasts more than a couple of weeks without charging, and it does charge with the same microUSB standard as most of my other devices (excluding the iPod Touch and the Nexus 5X), so it’s not too cumbersome while traveling.

A note on the picture: while the Accu-Chek Mobile has a much smaller and monochromatic non-touch screen, lots of its bulk is taken by the cassette with the tests (as it does not use strips at all), and it includes the lancing devices on its side, making it still quite reasonably sized. See also my review of it.

While the sensors store up to 8 hours of readings, the reader stores then up to three months of that data, including additional notes you can add to it like insulin dosage (similar to InsuLinx), meals and so on. The way it shows you that data is interesting too: any spot-check (when you scan the sensor yourself) is stored in a logbook, together with the blood sample tests — the logbooks also include a quick evaluation on whether the blood sugar is rising, falling (and greatly so) or staying constant. The automatic sensor readings are kept visible only as a “daily graph” (for midnight to midnight), or through “daily patterns” that graph (for 7, 14, 30 and 90 days) the median glucose within a band of high and low percentiles (the device does not tell you which ones they are, more to that later.)

I find the ability to see these information, particularly after recording notes on the meals, for instance, very useful. It is making me change my approach for many things, in particular I have stopped eating bagels in the morning (but I still eat them in the evenings) since I get hypers if I do — according to my doctor it’s not unheard of for insulinoresistance to be stronger as you wake up.

I also discovered that other health issues you’d expect not to be related do make a mess of diabetes treatment (and thus why my doctors both insisted I take the flu shot every year). A “simple” flu (well, one that got me to 38.7⁰C, but that’s unrelated, no?) brought my blood sugar to raise quite high (over 20 mmol/l), even though I was not eating as much as usual either. I could have noticed with the usual blood checking, but that’s not something you look forward to when you’re already feverish and unwell. For next time, I should increase insulin in those cases, but it also made me wary of colds and in general gave me a good data point that caring even for small things is important.

A more sour point is, not unusually, the software. Now, to be fair, as my doctor pointed out, all diabetes management software sucks because none of it can have a full picture of things, so the data is not as useful, particularly not to the patients. I have of course interest in the software because of my work on reverse engineering, so I installed the Windows software right away (for once, they also provide an OSX software, but since the only Mac I have access to nowadays is a work device, I have not tried it.)

Unlike the previous terrible experience with Abbott software, this time I managed to download it without a glitch, except for the already-noted geolocking of their website. It also installed fine on Windows 10 and works out of the box, among other things because it requires no kernel drivers whatsoever (I’ll talk about that later when I go into the reverse engineering bits.)

Another difference between this software and anything else I’ve seen up to now, is that it’s completely stateless. It does not download the data off the glucometer to store it locally, it downloads it and run the reports. But if you don’t have the reader with you, there’s no data. And since the reader stores up to 90 days worth of data before discarding, there are no reports that cross that horizon!

On the other hand, the software does seem to do a good job at generating a vast number of information. Not only it generates all the daily graphs, and documents the data more properly regarding which percentiles the “patterns” refer to (they also include two more percentile levels just to give a better idea of the actual pattern), but it provides info such as the “expected A1C” which is quite interesting.

At first, I mistakenly thought that the report functionality only worked by printing, similarly to the OneTouch software, but it turns out you can “Save” the report as PDF and that actually works quite well. It also allows you to “Export” the data, which provides you with a comma-separated values file with most of the raw data coming from the device (again, this will become useful in a separate post.)

That does not mean the software is not free from bugs, though. First of all, it does not close. Instead, if you click on the window’s X button, it’ll be minimized. There’s an “Exit” option in the “File” menu, but more often than not it seems to cause the software to get stuck and either terminated by Windows, or requiring termination through the Task Manager. It also keeps “prodding” for the device, which ends up using 25% of one core, just for the sake of being open.

The funniest bit, though, was when I tried to “print” the report to PDF — which as I said above is not really needed, you can export it from the software just fine, but I didn’t notice. In this situation, after the print dialog is shown, the software decides to hide any other window for its process behind its main window. I can only assume that this hide some Windows printing dialog that they don’t want to distract the user with, but it also hides the “Save As” dialog that pops up. You can type the name blindly, assuming you can confirm you’re in the right window through Alt-Tab, but you’ll also have to deal with the software using its installation directory as work directory. Luckily Windows 10 is smart enough, and will warn about not having write access to the directory, and if you “OK” the invisible dialog, it’ll save the file on your user’s home directory instead.

As for final words, I’m sure hoping the device becomes available in Republic of Ireland, and I would really like for it to be covered by the HSE’s Long Term Illness program, as the sensors are not cheap at £58 every two weeks (unless you’re clumsy as me and have to replace it sooner.) I originally bought the starter kit to try this out and evaluate it, but I think it’s making enough of good impact that (since I can afford it) I’ll keep buying the supplies with my current method until it is actually available here (or until they make it too miserable.) I am not going to stop using the Accu-Chek Mobile for blood testing, though. While it would be nice to use a single device, the cassette system used by the Roche meter is just too handy, particularly when out in a restaurant.

I’ll provide more information on my effort of reverse engineering the protocol in a follow-up post, so stay tuned if you’re interested in it.