Tuesday, 4 January 2011 | by Mike K

Active Insulin - Continuing adventures with the Accu-Chek Expert

Well I've been using the 'Expert' for a few weeks now and I'm pretty pleased with it. It took a while to get the levels set up right and to understand how it was making its calculations but as of now it's making some pretty good bolus recommendations for meals and more often than not I'm just confirming them.

In a little while I'll do more of a full review with a slightly more considered account of my experience, but I'm investigating a slight oddity at the moment and want to get my head around it before I write that.

There is a line on the Expert's display which reads 'Active Insulin'. According to the blurb this gives you an estimate of the amount of working insulin you still have on board based on the timing of your injection and the figure you provide for insulin duration (in my case 4 hours). Except that it isn't doing that. Well not for me anyway. In the first week I can dimly remember seeing Active Insulin numbers which matched quite closely to what I would expect. At least once I tested after a meal and thought, "Well it's a bit high but I've still got a unit on board so it will come down into range soon enough."

Later I began to notice some very low 'Active Insulin' readings around 2 hours after a meal which did not seem to correspond with the amount of insulin that really was active at that point based on what my BGs did subsequently. Over the weekend I ran some tests to try to work out what sort of curve the device was using to plot the fall-off in insulin activity. I wondered if it was weighted to having a higher proportion of the dose being used up in the first few hours. This does not seem to be the case either... In three separate tests the Active Insulin was displayed consistently as either 0u or 0.1u at 30 minutes, 1 hour, 2 hours and 3 hours after a confirmed bolus of 4 or 6 units.

I've emailed my DSN to see if anyone else has had this problem. I may also drop Roche a line to see if they can shed any light on it.

I'll let you know if I hear anything.

Update: Active insulin explained - read the 'comments' below

Update: Accu-chek Aviva Expert Review - One month in


Rob said...

Hi Mike,

Rob from the diabetes support site here. Just to add a couple of my comments on the Aviva Expert.

I agree that the 'active insulin' figures look a bit strange. I had 20 units about 45 minutes ago and mine is now telling me I have .5 units still active. Makes no sense to me at all.

One other thing that I think is horrible about it is that you can't set carb ratios using decimal places. I think my ratio at lunchtime should be about 5.7 but if I'm limited to whole numbers and have 100 CHO then it's going to be limited to recommending either 20 units (@at 5 per) or 17 (@6 per). Now that just can't be right.

Mike said...

You've pretty much summed up my (still unwritten) review right there. With a few minor tweaks this could have been a brilliant thing. As it is it's just OK, which is a real shame.

By the way... 'Active insulin' is a misnomer it should be 'Active correction'. It ignores any insulin connected with carbs in the meal entry and only regards any 'correction' element of the dose. If you want to track the whole bolus you need to back out of the bolus suggestion screen, then input the bolus via 'Add data'. I did that for a week but can't be bothered now.

Silly really, they should have made 'include meal bolus in active insulin' an option via a setting or checkbox somewhere. It must confuse everyone!

Rob said...

Ah, got you. Very counterintuitive.

Another couple of things I'd pick out are where, in the paperwork, it starts talking about entering basal figures. Very unclear (at least to me) what the idea is there.

And my favourite were their descriptions of 'snack size', 'acting time' and 'offset time'. What language do you think those were written in before being translated to Inuit, then Polish, and then back to English?

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