PDM Issues with BG Readings

Diabetes Technology Insulin Pumps
1

Hi:

Has anyone had issues with the PDM showing that you are low and then when you double check on another freestyle meter it says you are not?

I'm wondering if my PDM has a problem. Last friday it kept on saying that I needed to correct my low blood sugar, which I did. It kept on saying it was low all day long, and I did not feel like it was low.

I took out the freestyle regular meter that was sent with my starter kit and compared the two. Well the regular freestyle meter said I was just fine.. while my PDM kept on saying I was low. I checked the strips and thought that might be the issue. So I changed out the strips and then both machines did match.. I was no longer low. So I thought this problem was worked out, but then again today my PDM is saying 79, and my regular freestyle meter is saying 111??

Is this normal for two meters to say two different things? I'm just concerned that I may be treating lows.. when I really don't have a low.

Thanks!

2

There's been a lot of discussion here about that issue. Most do feel the PDM does read low, but usually it can be worked around. Search here for more on that discussion.

3

Yes! Yes! Yes! I have the same problem. Even tested the PDM meter against 2 other freestyle meters with the control solution. The PDM meter came in below the acceptable range listed on the test strips for control solution testing, while the other meters were well within range (so it's not the test strips). The PDM is definitely telling me I'm low (say 59) when I'm actually 99! If you didn't know, you'd treat for a low you didn't really have and end up high! I contacted Omnipod about this issue and got the impression there are definitely others who are reporting the same problem. I got a replacement PDM and it's doing the same thing! I think everyone using the new Omnipod PDM and relying on its meter should test it out with the control solution. I worry about children whose parents may be feeding them lots of carb to bring up false lows. I think this is potentially a very dangerous situation. I plan on continuing to use the stand alone freestyle meter because I can't trust the one integrated in the PDM.

4

You can trick the PDM into giving correct results. Change the code so that the PDM reads close to 104 mg/dl for the control solution. For some people code 17 does it, for other 18. I use 19.

5

Thank you for the tip! code 19 seems to doing the trick!

6

yes, this is one of the reasons i don't like the omnipod, pdm, it always reads so much lower then any of my meters and CGM. I turned the strip code up from 16 to 18, some use 19 (seems to adjust about 10 points per change). This makes me nervous, too. I also am a bit confused about the IOB feature.

7

What do you need to know about IOB? It's basically a calculation of the insulin that remains in the blood stream from your last bolus. Insulin is not an instant thing, it takes a couple hours to do it's job. This helps keep you from over-blousing and accidentally putting too much insulin into your body causing undo lows. Like for example, after some meals you might be high for a short time after eating while the insulin works on your food intake. If you were to do a BG reading at that time, without knowing how much insulin is already in your body at the time you'd probably give more insulin resulting in an eventual low BG. Does that help? Or were you looking for another answer to a different question?

8

Scott covered it qualitatively. Here's the math for those interested:

The Omnipod PDM uses a linear model for insulin clearing. The rate of clearance is based on the Duration of Insulin Action you set on the PDM. For example, if you set it to 4 hours, then the device will calculate that you still have 75% of a bolus active after one hour, 50% after 2, and so forth.

So, if you bolus 8U with a DIA of 4, one hours later the Omnipod will report 6U IOB.

It starts to get complicated when you stack boluses, which is easy to do with a pump. Say, for example, you take a correction bolus at 11am of 3U. Then an hour later you bolus 5U for lunch (ignoring the stacking issue because in theory all the meal bolus will be consumed by the food carbs).

What is your IOB at 1:00? The 3U is now 50% depleted, leaving behind 1.5U on board. The lunch bolus is only 25% depleted, leaving behind 75% * 5 = 3.75U. So, the PDM will report you have 1.5 + 3.75 = 5.25U IOB.

While stacking is generally frowned upon by the care community (it's very hard to manage and gets very complex with MDI), pumps really take most of the risk out of stacking, so long as the pump's settings are right for you personally, AND you're not having a weird day -- sick, stressed, etc. -- making insulin work differently that day.

The PDM takes care of all the book-keeping and calculations for you. Just make sure to test with a finger-stick for any boluses -- correction, food, etc. (okay, I cheat and rely on my CGM reading when I have reason to be confident in it's reading), and enter that BG value in to the pump for calculating dosing.

9

This is interesting. My PDM and the Freestyle meter sent (as a backup I presume) are always within a few points of each other.

This is what I'd expect, as the technology comes from Abbot Labs, not Insulet. I just assumed the same electronics that handles the assay of the blood is identical in the PDM to other Freestyle meters (one would think in particular the one included with the starter kit, eh? :-)).

IOW, there shouldn't be a possibility for differences like this, unless there's a defect.

OTOH, this is all speculation. Maybe Abbot deliberately cripples the Omnipod PDM to encourage us to buy more Abbot products. (I really don't think so, just had to throw that in for the conspiracy theorists).

Anyway, if my PDM was that inaccurate, I be a burr in Insulet's sock until they sent me a replacement. I would not accept anything other than acknowlegement that the PDM they sent me was defective.

Indeed, if you cross-check the PDM against a Freestyle meter, and at least one other manufacturer and find it is way off both, it is by definition defective. You have a right to a new one.

10

I'm starting to really believe it is defective, and I think I shouldn't have to up the code all the way to 19 on my strips in order to get the PDM to work correctly? I find it extremly tiresome to have to constently check my BG on the PDM and then check it on the freestyle to see if they are the same or within a few points of each other. Just yesterday, they were 50 point difference.. how in the world am i to correct my BG if I can't rely on the PDM? I'm going to call them when i get home from work and see if they can get me a new PDM. I'm still waiting for the replacement pods to replace the 3 pods that failed on me. Sigh... i love this device.. but would sure like it to work the right way!

11

The only time ever that I saw a 50 point difference was when I did not wash my fingers. If you see such inconsistency with clean fingers then something is definitely wrong.

12

i found this too with my PDM. I had to turn my code up to 19 too. I was gonna do 18 but 19 seems to work with my other meters and CGM. This all makes me so damn nervous. We have enough to worry about without the additional 'stress' of worrying about our PDM not being accurate. It was about 50 points off for me too. I don't think it's a PDM defective, it's just the meter is wrong. Please, will you post after you speak with Insulet...i'm curious as to what they say about this meter/coding issue. THANKS!

1 Like
13

You shouldn't have to (nor should you) set the code at anything other than what's printed on the bottle of strips. If you do, then the meter's defective.

Not sure exactly how the code value figures in to the assay calculations, but what I do know is it's not a simple, linear function. So, changing the code and getting the value "right" at a particular BG, like 100, doesn't ensure that at that wrong code input the reading is therefore also equally accurate at 80, 120, 150, 200. For example, the code might be representing some multiplier for that batch of strips -- rather than an offset -- compressing or stretching values around the one you targeted, making everything increasingly inaccurate the farther away you get from the value to targeted with the code tweaking.

Set the meter up as designed. If you are getting bogus results, it's defective, and Insulet should replace it. It's warrantied. The manual states the spec'd accuracy of the device... If it's consistently outside that specification, it's bad.

14

Oh, one more thing! This one bit me, and is probably obvious to everyone, but just in case...

There are two different types of FreeStyle strips, and they are not interchangeable. "FreeStyle", which work in the Omnipod, and "FreeStyle Lite", which do not.

If you use the latter in the meter, it will pass a control test but be way at the extreme low end of the range. This will fool you into thinking that, well, it passed, so must be okay.

NOPE!

Every test will read 20-40 pts low. Had myself panicking thinking I was running 50 when I was really 80, wondering why I was all of a sudden hypo-unaware (I have strong hypo reactions starting in the 60s), etc.

The FreeStyle strips compatible with the Omnipod are labeled with very fine print, "Use only with FreeStyle and Omnipod systems". Make sure your bottle has that on it.

15

it's not a defective PDM...it's the meter reads way lower then any other meters I have and my CGM too. As noted by others, about 50 points. All freestyle meters, it seems, are much lower then mine. My endo uses a freestyle and it was also way lower then my meters/cgm and from my blood draw blood glucose lab results (when we tested it).

16

I called Insulet and they are having me record what readings i am getting, then if it happens at least three more times they are going to replace my PDM. Of course, as of yesterday it hasn't been happening... has me scratching my head... don't know if i got bad strips from my mail order?? I just started a new bottle yesterday and compared the PDM to the freestyle meter.. and they were within a few points of each other.. very very strange..

17

Heh, and that is a problem for sure... my insurance will not cover the regular freestyle meters, even though it is built into the omnipod. They will only cover the freestyle light strips. I was also told by insurance that their coverage will only run from June 2013 to June, 2014 and then they will drop all coverage of all freestyle products.

Makes D life a bit unbearable at times.

18

I'm not doubting your experience, just challenging your interpretation.

Think this through for a moment... Do you think Abbot Labs would be able to stay in the meter business with accuracy like that? Which is, BTW, way outside the published specification for the device?

The FDA would pull the device(s) from the market immediately with that sort of unreliability. People are depending on these things for the life and health.

I have a stable of meters (as most diabetics do), and they all ready +/- 15 of each other, every time I've cross-checked. This includes OneTouch (several), Walgreen generic, Walgreens Tru2Go, Bayer, and the two FreeStyles (Omnipod and the backup shipped with the starter kit).

So again, I must insist that if it's consistently as far off as you say, then it's defective, and you should demand a replacement.

My Omnipod tester seems incredibly accurate -- more so than several of my other meters.