Paradigm RT: Accuracy & Placement

It's been three months since I hooked up to my smokey Paradigm 522 and its continuous glucometer, and I've learned a good deal during that time. My pump also did a bungee-jump off of my waist into the toilet...but that story is better left for another day. Or never. The jury's still out on that one.

The TGMS (telemetered glucose monitoring system) and I have a real love/hate relationship, moreso than I've ever had with my pump. Unlike my pump, however, I can take a break from the TGMS when I feel like it, whether it be for hours or a few days. I just remove the sensor and the seven billion layers of OpSite and stash the transmitter in my supply drawer, and I'm free without any repercussions. Err, well, except for the fact that I now have to consciously remember to do 12+ manual tests a day, whereas before it was routine. Amazing how quickly and easily good habits can be changed, isn't it?

To date, my largest complaint about Minimed's TGMS is the placement factor. Though the sensor/transmitter unit is really not that large, placement of the transmitter can be a real issue. I can put the sensor anywhere...but then I have to think about the three or so inches to the transmitter itself (the oval disk that sends interstitial BG readings to the pump every 5 minutes) and anything that might interfere with its mechanisms.

Transmitter Placement Problems

Girls who wear fitted clothing will get this one. I favour my upper abdomen for site placement of the sensor because I rarely wear my infusion set in any part of my stomach. Great, lots of room, right? Not so much...if I go too far to the mid-area with the sensor, then the transmitter is a big lump under a chic blouse or tight shirt. I've learned to tuck the transmitter up under my breast in order to hide it, but then the bra doesn't fit quite right (I'm well endowed). So I started inserting the sensor closer to the side of my rib cage, and tucked the transmitter either around my torso towards the back, or directly underneath the sensor site (remember, too far toward the belly button and it's obviously visible, especially under light shirts where the grey of the unit peeks through). The first time I did that I was woken up five times throughout the night to a nice "Weak Signal" alarm. If I sleep on the transmitter itself, or even sit on a couch with the unit pressed into cloth, the RF signal is lost.

So I moved on to my lower abdomen, trying it once and then never again. I favour low-rise slacks/jeans/etc. which are not conducive to placement of either the sensor or the transmitter. And using my hip caused the same interrupted signal problem as the sides of my upper abdomen.

Next in line was to try my upper arm. The clear winner, by a long-shot. I bring the transmitter up towards my shoulder, mid-line, and I haven't lost the signal once. And unless I'm walking around in a sleeveless shirt, the transmitter is completely inconspicuous. However, the obvious obstacle to placement of the sensor on one's arm is the placement itself. I just can't do it one-handed. Hold this while removing that and peeling layered tape...it requires two hands, no less (hell, sometimes three would be handy! *pun intended*). I can proudly insert any infusion set in my arm, even the Silhouette and sets with no injector, but I cannot see my way around a five-fingered job on the TGMS. So every time I want to put a new sensor in my arm, I have to have help. And since I don't always have help, arm sites are few and far between.

Accuracy

Everywhere I look, people are having accuracy problems. Or they're criticizing the accuracy of the Paradigm RT system (Enter Soap Box Rant: I'm irked by the people on the www {Note: the OC is not included in the aforementioned www} who have not even used the Paradigm RT system and yet are bashing it left and right and five ways 'till Sunday. Let me say this nicely. You've never used it. Please refrain from vocalizing your critical opinion on a technology that you are not personally familiar with. Especially when you are presenting blatantly incorrect information. Bugger it. Shut the hell up, you. What the hell do you know, moron? You don't even take the time to gather the correct facts {read: quit your damn day job} before spewing them all over the place. You haven't even used the damn system; don't knock it 'till you try it! Then you can bash the hell out of it if you feel so pessimistically inclined. Soap Box Rant Concluded. Please come again.). And though I don't deny that I've heard my fair share of accuracy issues by RT users - resulting in the obvious conclusion that the system still has many a bug waiting to be squashed - I personally have had very few accuracy problems during the past three months.

90% of the time, the sensor is reading within about 0.8 mmol of my glucometer, no matter what my blood sugar level is. High or low, it's not off by much. On average, I see a 0.3 mmol discrepancy between the sensor and manual BG tests per day (full day averages of sensor values compared to the glucometer value for a one month period). Interstitial lag time, possibly? Or could it be the simple fact that I am very well controlled, with few fluctuations, possibly resulting in a lower error grade from the sensor?

Alas, I am not an expert on this subject, so I leave it in the hands of Medtronic's R&D department. All I know is that the remaining 10% can mostly be blamed on my own self. Sensor insertion errors are generally the cause of any readings that I've had that have been +/-2.0 mmol outside of manual BG's. I've learned that I can calibrate the sensor successfully on a low or high BG as long as the ISIG (the signal strength value between the sensor and the pump) is above 5.00. And the one day of totally wacked out sensor readings (they were up to 4.0 mmol higher/lower than the glucometer pretty much all day) that I experienced was corrected when I removed the 10 day old sensor and inserted a fresh one.

Which leads us to the conclusion that the value of the RT is not in the values themselves - as Caro so eloquently put it - but in the trends that those values project. Up is up, no matter what the number may be (and vice versa), which is significant in pinpointing which basals and ratios need to be tested, and when.

But I also find great value in the flexibility of my own testing, as I've mentioned before. I can trust the TGMS enough to not have to manually test on my knees under a restaurant table (unless I feel the need to) or in a dark movie theater.

And that, in itself, is a small freedom that is large enough to hold on to.

Comments

[Keith]

Thanks for blogging about this Tiffany. I find it very informative and look forward to procuring a CGMS in the near (12 month) future myself.

Sorry your CGMS presents such a fashion challenge to you. Obviously this is not a big issue for us guys who could easily cover ours with a standard Tee or dress shirt. On the other hand maybe this will breed a new generation of men that find a CGMS peeping out from underneath a gals belly shirt alluring.

Hey, soap box rants are OK. I too find myself enraged by other's attitudes on various issues in D-land. Many times I just can't find the words to express myself eloquently, civilly and suitable for a PG rated audience.

Thanks again and keep up the good work!

[Scott K. Johnson]

Hey Tiffany,

I agree with Keith - I find your information and opinions on this and other D topics very informative and entertaining to read.

I too hope to get my hands on a CGMS sometime in the pretty near future - but it's still out of my reach financially.

Thanks for sharing!

[Gina]

Tiffany,
Thanks for sharing this info, its pretty funny how you explain things lol

[Jamie]

Hey Tiffany. I just got the recent Canadian Living Mag for October and they have a little page or so blurb about pumping insulin - more specifically, the combined cgms/pump from Medtronic. They started quoting prices of these things and how much the supplies cost. It mentions that you have to replace the sensor every 9 months and that it costs $7400 (or was it $7300?? At that high of price, what's an extra $100????) to do this.

Is this correct?? Or was it an information error on their part? That's one hefty price to pay for not even a years use of it. I really hope Manitoba follows Ontario and Quebec and starts paying for these things *sigh*.

[Sarah]

Thank you so much for this! I love hearing "real" reviews about these things. This is the system I'm hoping to get for myself, if I can manage to get my insurance to pay for it. With them currently covering a ton of strips per month for me and my problems with reduced hypoglycemic awarenes, Im hoping we can pull it off! Your information is good information, and something that is impossible to find on the medtronic sight! Thanks!

[Tiffany]

Thanks for all the comments, guys :)

Keith,
Now there's an idea; some day soon I will be walking along in a bikini, transmitter proudly displayed under my breast, and some guy's eyes will pop out like Wile E. Coyote in TGMS lust. I will ask myself: does he want me for my body, my smarts, or my TGMS?
(MWAHAHA Thanks for the laugh!!)

Jamie,
I am going to have to go out now, buy the Canadian Living magazine (honestly, I never liked that one) and send them some hate mail! My pump trainer has assured me that a lot of users are seeing transmitter lifetimes of over 12 months. And the $7400 (yes, I believe it's that number) is the initial cost that includes the new 522/722 insulin pump along with the transmitter. I already had the 512 pump, so I paid $1100 to upgrade to the 522 and get the transmitter. The base cost of the transmitter itself is $600 CDN.
Oh, I hope Alberta follows in the footsteps of Ontario as well! And it looks like BC is covering the cost of insulin pump supplies (at least for kids).

Sarah,
Good luck with your insurance company! I am always hopeful that, since Canadian insurance companies are covering the cost of the sensors, the US will soon follow suit!

Gina,
Is that funny ha-ha or funny weird? lol... ;) I'm here every week, tomatoes allowed!

Scott,
The financial thing is definitely a common problem. Good luck and thanks for the compliment :)

[Jamie]

Ahhh, thanks for clearing that up. After seeing $7400 every nine months in print, $600 doesn't seem so bad lol. And that's great that the transmitters are lasting longer than 12 months - good to know!

[Jamie]

Oh, forgot to mention, Manitoba does cover the cost of pump supplies, just not the cost of the actual pump (which, of course, is THE most expensive upfront cost). Fingers crossed about that being covered someday soon.

[Kerri.]

Great post, Tiffany. I haven't had any personal experience with a CGMS, but reading your detailed accounts really gives me a good glimpse of what it would be like to wear one, if I made the leap.

Thank you so much for all of the great information. :)

[Eric]

Tiffany,

Interesting post, as usual. Thanks. Your experiences with the CGMS accuracy are fairly similar to my own with the Dexcom unit; I see posts of people having accuracy problems, but personally, when I've had problems I can generally attribute them to some particular cause.

Now that I have a Minimed 522 pump, I wish that Minimed could reduce their transmitter to the Dexcom size - then I'd switch in a minute so I wouldn't have to carry around two different units. Maybe in the next generation...

[Tiffany]

I wasn't aware that Manitoba covers the cost of pump supplies, Jamie. I wish they'd start doing that out west!

Eric,
I have heard through the pump-gossip-grapevine that the next transmitter version will be smaller. Though I prefer the design of Dexcom's unit (smaller, no wires, and all-in-one) I, personally, much prefer not having to carry another unit and being able to bathe and swim without having to cover or remove the sensor/transmitter. But that's just me :) It's a trade-off!

[Jamie]

Oops, my bad - Mb will cover the pump supplies once you've reached your deductible ..... which probably doesn't take long when you're purchasing pump supplies (and all other diabetic supplies as well).

[PrintCrafter]

I wear the stand-alone MiniMed CGM (Guardian) and a Smith's pump--long story. Anyway, I like to wear my sensors on my legs. I wear tightish jeans, but the bump of transmitter has never caused me trouble or comment.

[Tiffany]

I wear the sensor on my thigh as well, Will; it works awesome there. Even with tight-tight jeans... ;) But people have asked me what it is, and I'm more than happy to explain. Usually their either really interested and want to know more, or they're totally freaked out and want to run away...