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Old 16-02-2013, 17:25 PM   #1
trophywench
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Roche Combo Meter vs Accu-Chek Expert
Here's an observation I'm really probably intending for Mike, although it may be of academic interest to anyone!

He maintains that the Expert meter he had, when calculatiing IOB, only showed any insulin taken as a Correction dose when his BG reading wasn't in range; if he just took 5u because he was eating 50g carb and his ratio was programmed in as 1u per 10g carb - 2 hours later it showed Zero IOB. However if he also took a Correction dose at the same time, it would show an amount of Active Insulin so small it couldn't be related to the entire amount of inslin he took at that time. He queried this with Roche at the time as it seemed odd, and they conformed his deduction was correct.

I've said for ages I thought the Combo meter took all the insulin into account,and I've been meaning for some time to note what the Combo meter does, bearing in mind it's kind of much the same as the Expert. Or it appears to be .....


My ratio is 1u to 10g, and the time my Novarapid is programmed to last within the settings of the meter, is 4 hours.

At 13.24, my BG was 9.4 and I was going to eat 50g CHO. Meter calculated 6.2u so that's 5u for the carb and 1.2u correction.

At 15.59, my BG was 9.3 and the meter said I had 0.6u Active Insulin.

Sooooooooo - 6.2u divide by 240 minutes = 0.02583u per minute, yes?

Multiply by 24 minutes = 0.6199 units.


So it appears the Combo meter does NOT have the problem he found with the Expert.
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Old 16-02-2013, 21:18 PM   #2
everydayupsanddowns
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Thanks for that TW.

I must fire up the ole Expert and offer some readings from it to see what it reports for 'active insulin'
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Old 20-02-2013, 10:03 AM   #3
Dory
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TW,

I'm afraid I'm going to disagree with you on this one....my AccuChek spirit combi only factors in correctional dosages into the 'active insulin'.

I have often noticed that if I am just bolusing (without doing a test, therefore getting any CF bolus), I can turn the meter on within the hour (or other time before the 4 hour limit I have set like you) and it will record that I have no active insulin. Yet whenever I have CF dosage, you can guarantee that checking on the meter up to 4 hours later will show a figure next to 'active insulin' which decreases over time.

So certainly my pump only takes CF into account when working out the active insulin left in the body.
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Old 20-02-2013, 10:31 AM   #4
AlisonF
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That would drive me mad. Surely that apporach only works if you can guarantee that you always get the amount of insulin to carbs right. And certainly in my world things ain't that simple. So I need to know for example that of the 10u I took for lunch, 6 are still active which given I'm now a 4 and dropping was a bit too much. I'll treat the low more aggressively if I know I have insulin on board than if I don't, but if I understand you correctly you're saying it wouldn't give me that info unless it came from a correction dose. I don't understand the logic behind that at all.
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Old 20-02-2013, 10:41 AM   #5
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I find the whole insulin on board thing very confusing and I don't trust it, there are so many variables to take into account that my meter is unaware of. For instance the GL of the food that I have bolused for being the biggest one. I tend to pretty much ignore the Insulin on board reading, I know .....for me.... that Insulin peaks at 2 hours and tails off pretty quickly after that, in other words, I disregard any high numbers I may see given as insulin on board after 3 hours after bolusing. .....works for me.
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Old 20-02-2013, 10:43 AM   #6
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yep, it's very annoying. So for example (and this is a typical day for me):

I'll have lunch, say 42g CHO. My reading is within target so it gives me a bolus just for the food (of 6.0u).

1hr after lunch, i test and have an apple. My reading is a bit high. It gives me 2.1u for the apple and (e.g) 2.0u correctional. BUT - it shows my active insulin as 0.0.

2 hours after that, I retest as I want to eat a banana. THIS time, is shows me as having a factor in the 'active insulin' category - which, given the only difference between the apple and the lunch occasions is the CF dosage, must be attributable to the CF.

frustrating?!!!!!
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Old 20-02-2013, 11:31 AM   #7
everydayupsanddowns
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Well the Expert certainly only tracks corrections, so 'Active Insulin' is a complete misnomer. It should be labelled 'Active Correction'.

As an example I popped some batteries back in my Expert and rand the following as a 'test case'.

12.00pm Lunchtime.
BG 7.8mmol/L, Carbs 60g
Bolus advice suggested 7.5u for food and 0.5u correction
Pressed confirm.

1.00pm
One hour after I'd 'confirmed' an 8u bolus...
BG 6.5mmol/L (I'd waited 30 minutes before eating)
Active insulin: 0.4u

Given that my insulin duration is set at 4h on the Expert, this only makes sense if the Expert is ignoring any insulin allocated against food and only tracking the correction dose.

Very silly!
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Old 20-02-2013, 11:48 AM   #8
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i can't understand why it does that; perhaps because Roche's view is that foold boluses are used up immediately on the glucose in the blood and therefore there won't (or shouldn't with a correct ratio!) be any insulin flaoting around 'spare' in the blood??
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Old 20-02-2013, 11:54 AM   #9
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I don't know. I did ask the Roche helpline peeps when I phoned them about it.

Perhaps they are confident that their 'meal rise' and 'insulin duration' settings will be enough to avoid overcorrection with extra snack boluses within 4 hours, and worried about people panic-eating when they read 4u active with a non-spiky 2hr post-meal test (though still a load of food digesting).

I still needs re-labelling though IMO, because it certainly *isn't* an accurate reflection of active insulin in my experience. And it gets even more complicated if you add in manual boluses (because Active Insulin on the Expert does track those!)
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Old 20-02-2013, 13:24 PM   #10
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The Medtronic approach of showing all active insulin, no matter how you took it seems more sensible. Then you have a total figure to start with and can apply common sense as to what to do next based on what you know ie the GI level of the food etc
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