I’ve been wearing the new Dexcom G4 continuous glucose monitor (CGM) for almost two months now. Before that, I used the Minimed CGM with my Minimed pump for about two and a half years, so I come to the Dexcom not as a new user or a familiar user, but as an experienced user with allegiance to another manufacturer. The worst kind of user for a company, in many ways — so, while others have done a great job reviewing in detail the new Dexcom G4, I will focus on my experience with the new device as compared to what I have come to expect based on the Medtronic Minimed system. Notably, I am only two months in, so I reserve the right to change my opinions, but, thus far:
Hands down, the best part about the new Dexcom relative to the Minimed CGM? It hurts so much less. It’s not painless, but it’s comparable to a pump infusion site, whereas the Minimed insertion device looked like an evil harpoon, and felt like one, too. Even after more than two years with the Minimed system, every time I inserted a new sensor, I would stand there for a few minutes, mentally convincing myself that it wouldn’t be that bad, and that the pain was worth it, before finally pressing the button to send the giant need into my abdomen. And at least half of the time, it was that bad, and I ended up bloody and in tears.
The Dexcom, on the other hand, has a relatively slim inserted filament. The insertion device requires a slow, gradual insert, which is sort of strange, but arguably preferable to the single-button-push approach. Further, because the insertion device and sensor are so reasonable, I am able to wear the CGM places other than my abdomen, which I was terrified to even try with the Minimed. Thus far, I have worn the Dexcom on my lower back (worked all right, but sub-optimally; it was prone to getting knocked and jostled off) and my arm (works capitally). This ability to move the sensor around opens up my abdomen, which was getting bruised and scarred to the point of not being usable.
And when I say the site on my arm works capitally — I mean it. I have been using the Dexcom sensor for almost two months; my first sensor, on my back, lasted about 9 days. My second, also my back, about 12. My third sensor is on my arm. I say is because it’s still there– I’m in week six of wearing this sensor. And it’s still just as reliable as the day it was born. Granted, I have a history of getting long lives from my sensors — my longest Minimed sensor lasted about five weeks — but that was after two years of learning how to coddle the sensors. Six weeks right out of the gate with Dexcom? Awesome.
Now, this lessened pain would be enough to make me switch from the Minimed even if the Dexcom were less reliable. That said, the Dexcom is much more reliable than the Minimed. After two years with the Minimed, I had gotten pretty used to its quirks, and could often tell when it was likely to reflect my blood glucose well, and when it was likely to be off. I am still learning these things for the Dexcom, but the default behavior of the Dexcom seems much more sensitive to changes in my blood glucose. Little dips and changes that were smoothed out by the Minimed– which always seemed closer to a twenty minute moving average of my blood glucose rather than a point-in-time value– are more likely to be caught by the Dexcom.
When I originally chose the Minimed, one of the biggest deciding factors was that I was already wearing a pump, and didn’t want to carry around an extra receiver (which, at the time, was the fugly, egg-shaped Dexcom one). Switching over to the Dexcom, I worried about the extra burden of yet another device, but two months in, it hasn’t been that bad. The receiver was designed to look Apple-y, and it’s fun to show off the color plot of my blood glucose values to all my (admittedly geeky) friends. My first thought– and several friends have echoed this– was that it looks like an old, knock-off iPod. Beyond style, though, this means that the device is small and light, and I can carry it in my pocket. (As a point of comparison, I can’t carry my iPhone comfortably in my pocket, so smaller-than-my-pocket is an important measure.)
All that said, it’s not an old iPod, and sometimes that shows. Which brings me to…
Despite giving the initial impression of an Apple-like device, the Dexcom receiver proves more like a cheap knock-off when it comes to the things that make Apple device feel really well designed. The fake scroll wheel (designed to look like the patented Apple scroll wheel, I presume) is actually made up of five buttons. These buttons are sort of hard to press correctly because they are all connected and give no tactile feedback when pressed. Sometimes I press, wait for a few seconds for the screen to come on, and then realize I apparently didn’t press hard enough or in the right place. This, obviously, is not a big deal for a medical device– but this is exactly the sort of thing that makes the Dexcom receiver feel “cheap.” Similarly, the little slot for the miniUSB charger has a slide-over cover (which is a good thought), but the cover is hard to move back and forth, meaning I end up leaving it open all the time.
Style aside, one thing I had gotten used to with the Minimed was that I could easily scroll back in time and see previous glucose reads. This was especially useful if I wanted to calculate the slope of my ascent or descent. The Dexcom, however, obscures those values– I can see the most recent read, the plot of dots, and an arrow, but not previous reads. The arrows are helpful, but I want a more fine-grained evaluation of my slope, and I can’t get that with the Dexcom.
Of course, I could try estimating from the points on the graph. But that brings me to another qualm: the graph goes from 40 mg/dL to 400 mg/dL, with no option for changing that. With that expansive range, and no grid lines, it’s difficult to tell what 1 millimeter difference along the vertical axis actually correlates with in terms of glucose values– is that dot 10 mg/dL lower or 30? I can’t tell. Given that I spend most of my time in the lower half of that graph– and, frankly, if I’m in the upper half I’m panicking and not relying on my CGM anyways– I would much prefer to have the range shown be configurable, like the alarms. Or at the very least allow me to see the actual past values– but to give me a difficult-to-interpret graph and no numbers? Ugh.
I should also mention that, despite being more consistently reliable than the Minimed CGM, the Dexcom G4 is not perfect, and is not a replacement for a blood glucose monitor. During times when the interstitial glucose that the G4 is measuring becomes uncoupled from my blood glucose– during strenuous exercise, for example, or periods of rapid blood sugar change– the Dexcom reports what it measures, which is understandably distant from my blood glucose. This, however, is a problem inherent in the way CGMs are currently built, and may require new technology that relies on alternate sources of glucose to fix.
Because it is a limitation of measuring interstitial glucose, I forgive the Dexcom for its periodic diversions from blood glucose. However, there are some things I don’t forgive Dexcom for. Cardinal sins of technology. Which brings me to…
One of the things I was promised about the Dexcom was that their software and analysis tools were really helpful. Worlds beyond the Minimed software. That was exciting to me — I am an engineer and analyst by trade, and so I love graphs and numbers and statistics.
Does the Dexcom software live up to these promises?
I don’t know. I don’t know because when I went to the website to sign up and log in to upload my data, I saw instead a link to download the Dexcom software. “Uh-oh,” I thought, “Download?” And then I clicked the download link and was taken to a page with a single download button. “Oh no. One button. Why is there only one button?” And sure enough, when I clicked the download button, a Setup.exe file plopped itself onto my desktop.
My Mac OS X desktop, that is. I work with computers all day long. Between work and home, I have 32 GB of RAM, 5 TB of space (500 GB solid state!), and sixteen processors. I have access to three compute clusters, and I could spin up an infinity of Amazon EC2 instances if I needed them.
But I don’t have a Windows machine. Because this is 2013, and no software should be Windows only. Even Minimed had (after some time) a multi-platform web app– it was a crappy web app with Java applets, but it was at least a web app.
It’s 2013! I can send emails from my Kindle in the middle of nowhere, Finland! I can VNC to my computer at home from my iPad on an airplane! Cars drive themselves, for crying out loud! And you’re telling me you can’t make software that works on Unix systems? It’s not like this software is doing deep, complex stuff, either– you’re plotting data points and calculating trivial statistics.
Sure, Dexcom could argue that some 90% of computers still run some version of Windows. However, I would be willing to put money on the bet that the percentage of Mac users among CGM users is much higher, since you’re selecting for a higher-income, more-comfortable-with-new-technology population. Further, if you know you only have the resources to maintain one type of software, there is no reason not to build a web application in this day and age. Data security concerns have been addressed to death, and, hey, Minimed does it.
The greatest irony, of course, is that, as I mentioned above, the Dexcom G4 is clearly designed to look like an Apple product — and yet the software doesn’t work on the very products that Dexcom is imitating! It is incomprehensible to me that after so much time, money, and effort is put into building a device, Dexcom would embarrass themselves so spectacularly with the software.
Okay. Now that I have gotten that off my chest, let’s regroup and get to
The Take Home
If you’re a diabetic: if you don’t have a CGM, get one. Today. And if you get one today, it should be the Dexcom G4, without a doubt. In a few months, the new Minimed Enlite may be a competitor, but the Dexcom is pretty darn good today.
If you’re Dexcom: I know a lot of good web developers in San Diego County. Why are you not employing any of them?
Karmel Allison is science editor of ASweetLife. She writes the blog Where is My Robot Pancreas?.
Follow Karmel on Twitter (@karmel_a)