NEJM Tandem Closed IQ Study

Very beneficial results published in NEJM yesterday:


This is great news. I am looking forward to shortly downloading the new algorithm for my Tandem X2. Another game changer. It is difficult to believe that 45 years ago I was carrying around a glass syringe with surgical spirit in a steel tube.


First I am a little hesitant about letting a device control all insulin delivery. I also do not like the acceptable in range high.


What are your preferred control limits, @DonR?

I would prefer 70-160

My biggest concern is relying on ANY brand/model of modern-day CGM sensors, to control my pump. As much as I like my G5, no way would I let it control my pump. Just 2 days ago, I had a rare, sudden failure of a sensor that plummeted the readings to below 40. Had that happened at night, all basal would have been suspended. No thanks. The G6 is not perfect, as anyone who reads about it online, in any forum. I suspect the G7 won’t be perfect enough either. Perfect, 24/7 readings for a week or two, just doesn’t seem plausible.

ahhh, I see. Mine are set 70-180 in Loop. So, not quite as tight, but not far off. You run a tight ship, Captain DonR.

Out of interest, why don’t you set your range tighter? I would have thought that setting the upper end of the range lower would result in earlier but smaller corrections, and likely no increased risk of going low. I certainly understand why people target a wider range when they’re not looping (so you 're not wearing your fingers down to stumps inputting correction boluses ever 10 minutes!) but when loop is doing that for you where’s the downside?

I was also of this mind set for a very long time! How could I trust a sensor (I was using an earlier version of Minimed sensors, than a newer but not better and than Dexcom G4 oh yeah a GlucoWatch for awhile). Just never felt the sensors were accurate enough. When I was using the G4 I was still testing before any bolus happened.
But after seeing the presentations, videos and talks about the Beta Bonic pump, I became very interested. I mean they were testing these pumps on kids at summer camp. You can’t get crazier numbers than young kids at summer camp.
So after talking with a few different endos, I took the dive and got a Tandem with a G6 and haven’t looked back. My correction rate is currently 1:90 and carb ratio 1:13. So I’m kinda sensitive to insulin and really worried about it sending me crashing.
But one year in, and I have had no problems! I went months without testing and enjoyed it immensely! No urgent lows no super highs because the CGM lets me know what’s going on.
Just finished up a clinical trial and had to do a lot of testing. And even on the first day, it was pretty close. Sure there were one or two that were 30 points off, but I went with the sensor number not the meter number and had no problems.
As much as we think the meters are the holy grail, they can be just as inaccurate. We have all done those double tests, from same finger, same drop of blood and get hugely different numbers. Don’t get me wrong, blood testing meters are the biggest greatest advancement in diabetes treatment except for insulin. But these CGMS are getting better and better and for the first time in a very, very long time, I don’t think about my diabetes all the time. I just let my little system do it’s thing and I get to live my life with a big smile on my face.
And my smile gets bigger when I think about all those who are looping and all the pumps coming down the pipeline that will do all the thinking for us.
Sure cure would be much, much better but until that happens, I want easy!


Sensors may be getting “better” (which, given all the issues that people report with the G6 is a questionable statement itself), but they aren’t good enough for me to trust to control my pump. I’ve been using meters since 1992. If you had said meters aren’t all that great back then, I’d agree with you, but in 2019, I’ll never agree that a good meter such as the Contour Next is not to be trusted. If you poke a clean, dry finger and place the blood correctly on the strip,. you are going to get an accurate reading far in excess of the number of accurate readings from a CGM. In over 4 YEARS of testing on a Contour Next, I’ve had just two readings that were wonky and I’m not sure that they weren’t my fault. You enjoy your reliance on a CGM and I’ll enjoy my distrust of them to regulate my insulin delivery.

I would be willing to try tightening the range. I guess I don’t have any reason not to give it a try.