Medtronic Simplera. Is it really the “Simple Era”?

At ATTD in Florence, Medtronic were giving away their new CGM, Simplera, to those who wanted to try them out in their experience booth, and allowing us to start and use the CGM, if our phones allowed it. This is the new CGM that works with 780G and the InPen, and as we were told by the reps, it stands for Simple Era…

Many of use took advantage of this to give this new kid on the block from the 800 pound gorilla of the diabetes world a try. 

It’s a bit of a removal from Medtronic’s older CGMs, being a single piece disposable, much like the Libre and Dexcom’s G7 and derivatives. For size comparison, here it is side-by-side with the Dexcom One/G6.

It lasts for 7 days (as do other Medtronic sensors) which in a world where you get a minimum of 10 days from other sensors, and more realistically, 14, this doesn’t seem great. News from within the diabetes community suggests that this might not be forever, and that this is the first phase. There was feedback from others that have participated in clinical trials with it that they have tested up to 28 days. Will that even see light of day? Who knows?

As with most new sensors these days, it’s factory calibrated (Roche, are you paying attention?) but does contain the ability to be calibrated (which is well buried), but more of that later.

According to the rep that I spoke to when I applied it, you can start a new sensor 3 or so hours (presumably earlier) in the app and then it will automatically switch over to the new sensor. I’d planned to try this out, however, the sensor died on me overnight, with enough hours to spare that I was unable to.

The App

As you’ll see in some of the images I have below, the app is black background, white numbers, arrows and line. The contrast this creates is likely to be very helpful for those with eyesight problems. It does, however, use a static vertical axis with some very odd numbers showing. While you might expect to see something like 4mmol/l and 10mmol/l displayed, given Time in Range guidance, instead it shows from 2.8mmol/l to 22.2 mmol/l divided in to equidistant measures, and there’s no way of changing this or having it dynamically adjust. This means that in regular use, if your TIR is regularly in the 4-10 zone, you almost never use the middle third of the screen. It just seems a little odd. 

Alert limits

In terms of setting high and low bars/alerts, there have also been some interesting decisions. When setting a high alert, you cannot use an even x.x value, they are all odd, which means no 10.0 or 11.0, only 10.1 or 11.1. Whilst this is just plain weird, for some people it will freak them out. 

Trend Arrows

Being a Medtronic device, it doesn’t adhere to standard trend arrow information that’s used by nearly all the other devices. We’re used to a horizontal arrow marking limited deviation, diagonal up and down for some and straight up or down for a lot, with no arrow depicting that it’s unable to determine what’s happening with the sensor, and those arrows being based on the last five mins of data. Medtronic’s approach is shown below, with no reference to time frame:

Okay, there’s no standard right now, so we can forgive them for doing something different from others, except that what they don’t tell you in the Simplera manual is that the arrows appear to be based on the last 15 mins of data. Within the 780G manual, use of the Guardian four is accompanied by a description of the time period over which the arrows account for changes (20 minutes).

This means you can end up with nonsensical outputs like the one shown below. That’s right, an increase in glucose levels with a down arrow because the 15 minute trend is down (according to the chart above), but the last five mins meets the up arrow specification shown.

Then the subsequent reading, with a similar rise, has no arrow, even though over the five minute period you might expect an up arrow.

Whilst this isn’t deal breaking, it makes nearly all of the work that multiple groups have put into helping users work out what to do based on trend arrows redundant, as the Simplera app simply doesn’t provide the same information. You could even say that it doesn’t provide actionable information.

Calibration

Most people will be pleased to know that calibration can be done in the app, but it’s not the most obvious menu option to find. It’s buried in the Sensor menu, which is the Simplera shaped blob on the bottom bar, and then through a few clicks more. Obviously, now that we know that no arrow means flat-ish readings, this would be the time to calibrate. The video below shows how to find it.

In this example, like in many others with this particular sensor, it was (once again) reading low when it wasn’t. With no arrow, it seemed an appropriate time to calibrate. It’s not difficult to do, but my experience of calibrating has been mixed. The sensor read quite low on multiple occasions, and the first time I calibrated, it made no difference at all. It was only on the second attempt that it bothered to listen to me, it’s user. Once you’ve calibrated, you get a nice little blood drop on the tracking line.

Other app features

Another useful thing the app does is show you clock changes when, for example, you travel across a timezone. That can be helpful when travelling or at Daylight Savings Time change.

You can also scan back through readings on the home screen of the app to see what the line really meant, given the unusable vertical axis. This is also a helpful feature, not requiring that the phone is turned on its side, or a different screen reviewed.

It’s an incredibly noisy app, in that it reminds you every 20 mins when it thinks your glucose levels are low, which is highly frustrating when it’s reading a long way below fingerpricks and other sensors. You can mute alerts, but that’s for a max of four hours and doesn’t stop the urgent low from pinging you. It also pings you when the battery in your phone is at 20%, which may or may not be useful, as well as when it loses the sensor. You can turn off the notifications via phone settings, but the app gets a bit upset at that!

As we’ve found, from the point of being a usable receiver, the app does plenty, however, there’s a lot it doesn’t do as well.

What the app doesn’t do…

This being a Medtronic device, it requires data to be uploaded to Carelink, and provides no mobile interface to be able to access Time in Range data. Instead, you have to go to the monstrosity that is Carelink online. While I understand Medtronic’s desire to put everything into their walled garden, not allowing access to this data within the setting of the app seems like an enormous oversight. Given that you can find time in range data from other CGMs in the associated apps, or at least in a mobile app, having to go to a browser based system and then run a report that generates a PDF, just to look at your data, is crazy. This is a real “nul points” moment. If there’s one request, it’s “Please open up access to your data so that we can use it in systems that we like”.

Now the other view might be that this is really a sensor designed for use within the Medtronic Ecosystem rather than on its own, and the InPen app suggests that this is the case, giving just the type of reports missing from that of the Simplera. 

Indeed, the above report from the InPen app does everything that the Simplera app doesn’t. Similarly, I assume the same type of report is available on pump with the 780G. 

Performance

I’ve mentioned a few times already that I saw significant low readings compared to the Dexcom One I put on at the same time. I also compared a few times to fingerpricks, and while the One tracked pretty well, the Simplera regularly read significantly lower. In fact, if we compare the time in range data for the One and Simplera over the period, the two graphs below show that Simplera thought that I was low 11% of the time, with One showing 3%.

Frustratingly, even when I tried to calibrate around day 3, it reverted back to tracking low. 

An example of the difference is shown in the below picture, where the ONE and fingerpricks were very close, but the Medtronic device was a long way off. Unfortunately this wasn’t a one off. 

A later calibration proved more successful, but not until I’d had five or so days of incorrectly low readings. Speaking to others about their experiences, some saw similar to mine while others had pretty good tracking, so it’s possible this is a cross-batch factory calibration inconsistency problem. I have a second sensor (from the same batch) that I’ll try out and see where we get to. 

Others’ experiences

As we’ve mentioned, a significant number of people took advantage of the try-out. Feedback has been mixed, with the following themes coming out:

• Sensors working perfectly fine, with no issues;
• Sensors reading lower than they should;
• Sensors not lasting the full life;
• Failing very early after application;
• Skin reactions to the adhesive used.

All of these are things we see across other sensors as well, so it’s not like this is significantly different. 

What conclusions can you draw?

A one part sensor/transmitterthat works with Medtronic pumps and the InPen, and that can be attached easily with one hand is a pretty big step forward for users of Medtronic devices. Whether everyone is happy with the idea of losing the rechargeable (and therefore less wasteful) aspect of the previous set-up remains to be seen. 

For many, seven days still seems indecently short, and as a user of ten and fourteen day sensors historically, it would be good to see Medtronic get their longer lasting sensors out on to market. Whether those will come soon, we don’t know. Equally, there are serious questions about the commercial model if you replace sensors almost 50% less frequently…

As for other aspects outlined here? Well if you’re historically a Medtronic CGM user, I guess you’d be familiar with the various characteristics of their set-up, but I think there are some good reasons why other systems seem to have a larger market share when it comes to standalone CGM. The dependency on Carelink, for me, would be one of them.

Ultimately, I think it’s a step forward for ease of application in the Medtronic CGM ecosystem, but as a standalone sensor, it feels like a long way from the idea of a “Simpler Era” [sic].