This post comes from the category of "posts that never quite made it..." since the information in it and the intention to knock it into shape, has been hanging around for quite a while, but somehow it never quite happened. The original title would have been "Guardian RT: In a Single Sentence".
I guess, it has never been my intention to discuss the Guardian RT or continuous monitoring in great depth since so many others have already made an admirable job of this task: Life After Dx (of course!) discusses use of the RT, Tiffany over at Candid Diabetes has done a fantastic job of describing her experiences with the Medtronic 522 integrated pump and sensor, and Amy at Diabetes Mine is recounting her experiences with DexCom, following in the footsteps of the Insulin Factor's Matt Vogel. In short, there are plenty of capable voices out there.
I still wanted to take the opportunity though to try and sum up my perspective on the Guardian RT, which I used for just short of two months before my switch on Monday to the 722. This really is my perspective and my opinions and experiences. Continuous monitoring is definitely an area in which your mileage may vary. But, if I had to use just one sentence to describe this thing it would be:
The Guardian RT is a device that gives you prompts to test your blood sugar.
There is obviously more to it, but ultimately that, for me, is what it all boils down to. The Guardian RT has been able to replace some of the prompts that my body has no longer been giving me since my experiences with severe recurrent hypoglycaemia.
Low and High Alarms, or a series of readings that indicate I am trending sharply up or down are things that prompt me to do a traditional finger stick and treat as appropriate. The Guardian RT doesn't have the on screen grpahs and trend arrowns that both the 522/722 and Dexcom have, but scrolling back through the numbers and drawing a mental picture of where my blood sugar was heading was a frequent prompt to act. I couldn't tell you how many times in the last two months I've tested at times I would otherwise not have, particularly in the absence of prompts from my own body in the form of hypo symptoms, and I have found lows needing treatment and highs worthy of correction.
I've tended to find that the Guardian RT is spot on with my finger stick readings more than 90% of the time when the reading on the Guardian lies between 5 and 8 (90 - 145). Even at lower levels the correlation is great, provided that the lower levels have crept on slowly. Otherwise there will tend to be a lag of around 10-15 minutes. When my blood sugar is above 9 (160), the Guardian RT tends to be almost permanently off the number. These things reinforce that fact that the Guardian is best as an indicator of when to perform a traditional test. A conservative low threshold - around 5 (90) - leads to a test before the Guardian can get too far behind, and hopefully before blood glucose can get too low. Even if the Guardian and a fingerstick are spot on at that time, looking back over the trend on the Guardian and checking the next couple of readings, along with knowledge about active insulin on board and recent food and activity can help decide how to proceed. And knowing that a number of 9 or more is unlikely to be spot on is a definite prompt to test.
But, for anyone who finds that somewhat disheartening, there is more to it: The discrepancy with high numbers appears to be consistent. That is, the discrepancy is almost always the same. Between 9.5 and 11 (170 - 200), it is around 2mmol (36mg/dL) too low, above 11 (200) around 3-4 mmol (55 - 72mg/dL) too low [Bear in mind I haven't has that many readings in this range] This is really significant, because it means I can predict what my finger stick reading is likely to be based on the Guardian reading. The finger stick is needed to check, but the numbers aren't quite as useless as they may appear.
In fact, a good way to view the RT, or any interstital fluid continuous data, is removed from the numbers entiriely. The scale it gives out could be in pink elephants for all it matters, as long as you know what the numbers mean for you, and you know how you need to act and when you need to test based on them. Also, in my experience, even if the numbers are a little out of whack, the trend is almost always absolutely spot on.
I'm happy with that approach right now.
I totally agree with many of the statements out there - that continuous monitoring is not a magic wand to transform control. It is simply another tool, another layer of information that we can use in our quest to stay healthy.
To me, it certainly gives peace of mind. It is another pair of eyes to watch over me... prompt me to act. And it clearly shows patterns in a way the snapshot finger sticks can never do.
And the drawbacks...
Of course there are plenty.
In the case of the Guardian RT and the DexCom there is the inconvenience of carrying the bulky monitor around, and the risk of losing that monitor if you set it down somewhere away from home.
Continuous monitoring gives an awful lot of data and as Allison has pointed out, there is a tendency to get information overload. Some of the data may even be very surprising. I was totally floored by how little my blood glucsoe spikes after certain foods, having always assumed a spike was there. It takes time to shift the ingrained mindset for dealing with data from finger sticks, even the large number of fingersticks that many people seeking good control perform. There is a very real risk of becoming somewhat obsessional about the numbers and continually checking them out and following them. This in turn can easily lead to frustration when the flat line you aspire to in your mind's eye fails to become a reality. (Get real here: even people without diabetes don't get completely flat lines!) Not all the actions made based on continuous data will turn out to be the right ones and sometimes it is easy to regret intervening in a downward trend when it subsequently spikes up, or vice versa. But then, not every decision made based on any data will be correct.
On the other hand, there is a risk of becoming over dependent simply on the alarms, instead of listening to your body and remembering to use common sense and judgement. Oh, and checking out those trends!
Plus... the biggie... despite my discussion of accuracy issues above, things can go awry from time to time and the readings will go out of whack. This may be temporary - related to rapid changes in blood glucose levels not matched by changes in the interstitial fluid, or related to performing calibrations at a time when things are not stable. (I had a tendency in the beginning to want to tell the Guardian that it had got things wrong. "Damn you, stupid monitor. Look, my blood sugar is actually thiiiiis high." This is a mistake. It only confuses the unit more and sends things further out of whack.) Sometimes the sensor in use just seems to be a bit screwy. Either way, you know the solution: test,test, test.
There is no hiding from it.
Continuous monitoring won't reduce the number of finger sticks needed.
Hell, it may even increase the number performed!
(Coming up: Watch out for my High School Science essay standard 'Compare/Contrast' on my experience of switching from the Guardian RT to the 722)