Pumps and CGM - accuracy

[sallymac65]

Hi, Ive been using a pump for about 6 years or so, so Im comfortable with that technology. However Ive recently lost my hypo warning signs which is pretty scary quite honestly, particularly when driving. So Ive borrowed a sensor from my DSN which has been an interesting experience and havent slept well since. But my main query is how accurate are the results from the CGM - often it was saying I was below four but I felt absolutely fine. Has anyone else had experience of using a CGM but they werent sure of the results coming back to them? Id be very keen to know. Whilst the sensor was a good test, Im not sure at this stage if Id want to wear one all the time. Thanks. Sally

 

[sallymac65]

Just seen Ive posted this in the wrong forum, didnt know there was one for blood sugar levels as well, so apols until I can delete it!

 

[Engineer88]

No worries - yes Ive had this on the Dexcom. I tend to go between the monitor and the CGM so if Monitor said 7 and CGM 8 i would assume 7.5 (rough calc) what CGM are you using?

 

[sallymac65]

Hi, Ive been using the Freestyle Navigator one. I just find it weird though when I look at it, it warns me that I'll be going low in 15 mins, yet my level from a finger prick is above this. Confusing or what! Is Dexcom your pump then, or just your cgm? Sorry for ignorance, Im on a medtronic pump but not the new fancy one yet ....

 

[searley]

Do you take paracetamol ? I've been told that can mess up the results


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[sallymac65]

Hi searley, thanks for the response. No I dont, but do take ibuprofen sometimes, perhaps that would be similar? Any ideas?

 

[Julie1471]

Hi Sallymac65, from what I've read on some of the forums, their can be a difference between blood sugar test and cgm, but I can't remember how much. I've also read that the Dexcom cgm, can be a bit more accurate than some other cgm's. Dexcom is the cgm that can run along side a pump and one the pumps, that it works with is the Animas Vibe. I had the same problem when wearing a cgm, I found that I couldn't sleep, while wearing it. But I have no problems sleeping with my pump.

 

[Engineer88]

as Julie says it goes with the Vibe pump. Ibrufen does not affect fluids like paracetamol so not to worry. most CGMs are more accurate than meters (meters have to be within 20% of a vain result CGMs tend to be around 10%) and remember that can be +/- a reading on your meter of 7 could be anywhere between 5.6 - 8.4 when tested from the same sample in a lab. the same on a CGM could be 6.3-7.7ish. also your CGM isnt reading 'blood' glucose its intercell fluid. which is linked to BG but isnt quite the same (it has a lag)

If you feel ok go with that is the short story!!

 

[iHs]

Hi, Ive been using the Freestyle Navigator one. I just find it weird though when I look at it, it warns me that I'll be going low in 15 mins, yet my level from a finger prick is above this. Confusing or what! Is Dexcom your pump then, or just your cgm? Sorry for ignorance, Im on a medtronic pump but not the new fancy one yet ....

Hi

There have been some msgs left on the forum all about someone's experience with the Navigator (which wasn't that good) and caused no end of worry. Navigator said bg levels were lower, when bg level done at same time said a bit higher. Problem was when Navigator said hypo levels but bg meter said not and person didnt feel at all hypo. If you use the search facility at top of forum page and type in Abbott cgm or Abbott Navigator you'll be able to have a read of the msgs and then make your own mind up.

Some hospitals are now buying the standalone Dexcom cgms to give to diabetics on a loan basis.

 

[sallymac65]

Hi IHs, thanks for input and swift response. Ah I hadnt realised that there was such a problem with the freestyle, and I was told that it was the best on the market, it appears not from what you say. I shall do a search as you suggest, and very interesting to hear about the Dexcom as well. Cheers, Sally

 

[pumppimp]

Hi IHs, thanks for input and swift response. Ah I hadnt realised that there was such a problem with the freestyle, and I was told that it was the best on the market, it appears not from what you say. I shall do a search as you suggest, and very interesting to hear about the Dexcom as well. Cheers, Sally

Hi Sally, I have the dexcom and vibe, before I got it I did a lot of reading and found the dexcom to give by far the most accurate readings. I found the freestyle to have some of the least favourable reviews. All the CGMs on the market were tested during a trial for a closed loop system and the organisers said that the dexcom came out far above the rest, and that's why they picked it for their study.

 

[Platinum]

I have a Dexcom CGM and Accu-Chek Combo pump. They work really well together.

The Dexcom CGM reading is +/- 20% plus/minus the 10 minute interstitial lag. My BM (In extreme cases) can fall or rise by 1 mmol/L per five minutes or 0.2 mmol/L per minute. So if my CGM reads say 7 mmol/L my actual BM could be 7 minus 20% = 5.6 mmol/L minus 2 mmol/L for a rapidly falling BM over ten minutes which equals 3.6 mmol/L which is obviously a hypo.

Alternatively, I could have a rapidly rising BM so a CGM reading of 7 mmol/L could be plus 20% (1.4 mmol/L) plus the ten minute delay of 2 mmol/L giving a total of 10.4 mmol/L.

If the possible errors are kept in mind, it is fairly easy to get an idea of what is going on. The Dexcom manual even says that you should not adjust insulin or carbs based on its reading – You should always use your ‘proper’ BM meter to ensure accuracy.

For this reason, I only ever calibrate the Dexcom when my BM has been stable for at least 30 minutes.

The Dexcom software is really helpful – It is a FOC download.

 

[sallymac65]

thanks to all for your comments on this thread, I feel so much more well informed than I did last week, much appreciated.

 

[Stefano]

The main point with all the CGMs, as already stated, is that you should calibrate only when your blood sugar is stable. I usually check the last 20 minutes. Calibrating when your bg is rising or going low will give you not reliable readings. I have tried the free style navigator 2, following these rules, and I had great results. I also tried the Medtronic- enlite and I found it less accurate. I am interested to try the dexcom as, reading here, it seems to be the most accurate.


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