Abbot FreeStyle Libre, the mobile app

You may remember I reviewed the Abbott FreeStyle Libre and even tried reverse engineering its protocol. One of the things that I did notice from the beginning is that the radio used by the sensors themselves is compatible with the NFC chip in most cellphones.

This was not a surprise to everybody; indeed I was pointed at a website (which I refuse to link) of Nightscouters (self-proclaimed people who “are not waiting”), which in turn pointed to an unofficial Android app that is able to read that data. The app is unsafe though (thus the lack of links), as it does not wait the first hour to get a reading, and allows to keep reading the sensor after the two weeks provided by the manufacturer. Their excuse is that you should be able to get the data and judge by yourself; I don’t like that answer, particularly as the raw readings need to be normalized by the Abbott reading device for it to have a valid reading.

Indeed, the various groups I see proclaiming “they are not waiting”, are vastly interested in the idea of quantified self, rather than having an actual health need for this data. They would be harmless, if they didn’t suggest using similarly risky methods to gain information that could be used to make medical decision. But this is a topic for another time.

Instead, a few months ago, Abbott themselves sent out an email to the register users that they made an official Android app available. Called LibreLink, and developed by a company identified as AirStrip Technologies based in San Antonio, Texas, this app is able to initialize and read a FreeStyle Libre sensor from an NFC-capable Android phone. It can be used to either replace the original Abbott reader device, or in addition to it.

I have tried it as soon as I could, which meant not right as I received the mail: the app is only able to read a sensor that it either initialize by itself, or one that was scanned during the one hour window in which the readings are not available. I suppose this has something to do with the pseudo-calibration that the FreeStyle Libre system provides.

Having the ability to take my readings from the phone turned out to be a good thing. While I would still try to keep the readings on the official device, which allows downloading them to a computer, and provides a full PDF I can send my doctor with the history, it allowed me to forget my reader at home for a day, and not having to worry, or being able to take a reading during a meeting in which I did not think to take the reader with me. It also provides more information than the reader itself, including what Abbott calls the Ambulatory Glucose Profile (AGP), which ends up being a graph of 10-90 percentiles, 25-75 percentiles, and median.

Aside: turns out that getting used to read percentile graphs, which is something my dayjob trained me to do, made it much more obvious to me what the AGP graphs were; I had to correct the Diabetes Ireland website, that listed it as a set of superimposed graphs. It took me a good half-hour to realize that it was just obvious to me due to my work, which is totally unrelated to health-care, but it would not be so to a doctor who has not seen that kind of monitoring before. Cross-discipline information exchange is good.

Unfortunately, it seems like the app likes to share data with its developers. This makes sense to a point: science is progressing, and they want to know how exactly it makes your life different, does it make it easier to keep your sugar within limits? Does it make it more likely to get sugar-lows, rather than highs? These are all good questions. I have not tried investigating (yet) whether the app shares this data over a properly encrypted channel or if it’s an actual privacy risk. I might better not know, since it does scare me a bit, but I guess I should do that at some point.

Again as an aside, I did get myself an Android phone capable of NFC, for the sole reason of being able to use that app while inspecting its traffic. The phone I used previously for that is my corporate phone, so I would not be able to fiddle with the traffic dumping on it. But I guess I’ll have to find more time for that, nowadays.

While I have been happy that the app was around, it was not perfect either. In particular I have a bad feeling that it might have something to do with two sensors failing on me with an error I did not see in the eight months before the app was introduced. I have made the mistake of not contacting Abbott right away about them, which meant I thrown them out without sending them for inspection, I have since realized my mistake but could not risk causing more failures until about this month, since I’ve been traveling a bit, and it takes me about a week or two to get new sensors in Dublin.

The reason why I suspect this is related to the app is not just that I didn’t get those kind of errors before I started using it, but also because I had read of similar failures happening when using the unofficial app suggested by Nightscouters, though in that case it’s said to be dependent on the NFC chip used by the cellphone. The two things together made me suspicious.

I’m actually told (by both my doctor and Diabetes Ireland) that Abbott is meant to start selling the device (and sensors) in Ireland before next month. Right now they do have an Irish website, which is more than they had when I started looking into it. I do not know as of yet, whether my long-term illness coverage includes these sensors or if I’ll have to keep paying for them myself (at least the falling Sterling is helping), but either way it’s going to be simpler to procure them if one of them fails.

As a final note, I should probably write down my own impressions when the sensor failed, compared to the article Daniel pointed me at back when I posted about my experimentation with this CGM (pardon, flash glucose monitoring system.) Although the first time this happened, it was not due to the mobile app; instead the application packet for the sensor failed, and I “primed” a sensor without a needle.

This happened when I was in Lisbon on vacation, and I only noticed after the hour passed, and I was queuing up for a train ticket to Cascais. I’ll admit it: I started panicking. I did not plan for it and I did not want to be out and about alone without the sensor. Part of the problem was to be found in me not having the normal glucometer with me, so having absolutely no way to make sure I was okay. The panic probably would have limited itself had I managed to get a ticket in less than twenty minutes. At the end I gave up when I got to the machine and it refused to accept either my cash (too wrinkly) or my card (too foreign.) So I turned around, went back to the hotel and put a new sensor (yes I traveled with a spare.)

Would I have panicked like in the linked article? Maybe, but I would like to think not. When the sensor actually failed me at home, this time indeed possibly due to the app, I didn’t have a spare sensor at home, and that made me angry. But at the same time, I knew it was not that important, I lived without it before, and I can live without it now, it’s just more inconvenient. What I did was putting a new cassette into the Accu-Chek which is significantly nicer to bring around than the kit for the Libre-as-glucometer, and ordered more sensors. I ended up staying a week without the Libre; it bothered me but I didn’t change much of my habits: the Libre trained me on how to relate my sensory experience with blood sugar, and what I can and cannot eat when, so I felt fairly safe overall.