Here’s the text from the G6 “using your G6” guide; the only thing that anyone reads given that the user manual has 360 pages (sides):
"Chapter 4: Treatment Decisions
With the Dexcom, you can make treatment decisions without using your blood glucose (BG) meter (meter).
But sometimes you must use your meter instead of the G6. And other times it’s best not to treat, just watch and wait."
Then (the * * * indicate elisions by me for conciseness):
"4.1 When to Use Meter Instead of G6
Rely on your BG meter for treatment in these situations:
o G6 doesn’t snow both a number and arrow.
* * *
o Your G6 readings don’t match your symptoms.
* * *"
There’s nothing that I can find in that guide (I can’t speak for the user tome) indicating that treatment decisions should only be made if the G6 is calibrated except that it suggests that if the G6 is off from the meter (my G6 is currently running 20mg/dl higher than the meter) you should calibrate. In fact I know that the G6 is running high because it violated the second condition at one point; the G6 indicated 80mg/dl at one point my blood sugar was well below that. The meter did show 60mg/dl at that point although the meter (Omnipod PDM + FreeStyle strips coded at 16) is notorious for being low.
I admit that the DexCOM words above are both ambiguous (“you CAN”) and barely English (sentences starting with “But” and “And” and other cringe-worthy phrasing), but all the same the meaning seems clear.
This is my first sensor on the G6, I’m going to run it UN-calibrated until it self-destructs or fails, about 9 days on average, then I’ll try calibrating the next one. The only issue I see is that it took maybe a day to stablize; it initially read exactly the same as my meter (which probably reads low) so calibration in the first day would have been pointless.
Yes, there was a trade war initiated in 2013 as a result of the European threat to adopt the 2013 ISO standard. It started with some interesting data from Germany which was adopted by various Xenophobes in the US; the original data had more the appearance to me of an attempt to discredit a particular German manufacturer. Nevertheless the adoption of the ISO standard in Europe was delayed until 2016. It’s not clear to me when the new FDA recommendations go into effect; there is implication that they are apply to all new applications but that’s not explicit. Anyway, those recommendations certainly don’t apply to CGMs and the G6 certainly doesn’t meet them; I don’t think it even meets the previous (20%) recommendation though it might if the results weren’t bucketed.
The FDA approved the G5 for treatment decisions according to DexCOM (the link DexCOM give to the FDA web site is to a publicity document, not a formal approval letter). Here’s the diatribe article, it seems correct to me (given that I haven’t tracked down the formal approval document):
The FDA publicity stuff on the G6 is here but it only comments on the approval for closed-loop systems:
The BG meter FDA recommendation from 2016 explicitly applies only to patient use BG meters; everything else including CGMs is explicitly excluded. The above link shows that, at the time, (May 2018) the FDA had no formal guidelines for accuracy in CGMs when used in closed loop systems:
“[T]he FDA is establishing criteria, called special controls, which outline requirements for assuring iCGM devices’ accuracy”
Use of the present tense is intended to imply the corollary “the FDA does not have criteria…” Ah, English, don’t you love it.