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how many days is it before the G4 is reliable?

Discussion in 'Parents of Children with Type 1' started by ChaosRules, Sep 18, 2013.

  1. ChaosRules

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    I'm sure every sensor is different, but I'm just curious what you guys are finding as far as reliability. We're just not having good luck. I really want to like the CGM, but I totally understand why my son thinks it's worthless.

    Here are some numbers from the sensor that was started on Friday night. I'll put the finger prick meter readings in parentheses.

    Saturday 20 min after lunch: 68 and dropping (meter said 118)
    20 minutes later, G4 said 149 steady (meter said 105)
    evening G4 said 172 steady (meter said 127)
    late night G4 said 143 and rising (meter said 120)​
    Sunday night G4 said 76 steady (meter said 112)

    Monday mid-morning G4 said 174 steady (meter said 140)
    late night, 1 hr after snacking, G4 said 121 steady (meter said 173)​
    Tuesday an hour after lunch, G4 said 59 steady (meter said 82)


    Also, it doesn't seem to understand calibration the way I do. :D Just now, the G4 said 136 steady, and the meter said 138. Woohoo! But after entering the 138 as a calibration, the G4 said 136 and dropping. Doesn't make sense to me.

    Is this pretty normal for the G4? Are we just expecting too much from it?
     
  2. Lizzie's Mom

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    Try to resist re-calibrating Dex if the number is less than 10% off or numbers are going up or down rapidly (unless Dex is displaying a blood drop icon requesting the calibration).

    The reason is that when numbers are changing rapidly (up or down), Dex is 'catching up', and calibrating just 'confuses' it. Wait until numbers have leveled out a bit; test, and then calibrate if needed. You'll find more accurate numbers overall if you are considerate of Dex's wonderful but somewhat limited 'brain' ;).
     
  3. swellman

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    Where are you applying the sensor?
     
  4. ChaosRules

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    Yeah, we're doing exactly what you recommend. If there's anything but a straight arrow, no calibration. If the numbers are reasonably close, no calibration unless the G4 is asking for one.

    Probably calibrated too often on Saturday, though, in an overzealous attempt to make it read accurately.
     
  5. ChaosRules

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    Abdomen, to the side and slightly above the belly button this time. No scar tissue, not in the way of clothes.
     
  6. mmgirls

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    Does he take any meds that could be interfering?
     
  7. swellman

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    Firstly, anything immediately after eating I would throw out - there's a lag between rapid rises and falls and I wouldn't compare BG to BG against a meter.

    Secondly, a 140 vs 170 I wouldn't sweat too much and just calibrate and move on. Same for 140 and 120.

    Additionally, the 68 and dropping could have been somewhat predictive - we've seen this. We've also seen where we have had erroneous lows that I have attributed to improper calibrations.

    I would refrain from entering BGs when BG is rapidly rising or falling and when the BG is within 10-15%.

    Lastly, the most valuable information on provided with the meter is the relative direction of BG coupled with the knowledge of how much insulin in on board.
     
  8. Beach bum

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    Yes, we have seen this. We had one recently where the CGM alarmed at 90 (our # for lows), when we clicked it said she was in the 80's. We checked on the meter, said she was around 100. Within about 5 minutes it alarmed again, she was 53. It happened so quickly the meter lag just couldn't catch it.

    We are participating in a study and we cannot calibrate if it's 2 arrows up or down or of it's a rapidly rising or falling number. I tried once to see what would happen and it really was a waste of a strip and blood. Numbers weren't even close.
     
  9. Mish

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    Another piece of the puzzle: what blood glucose meter are you using and are you sure that it is accurate? Have you done a control solution test recently? Test strips not expired? They haven't been stored in a car, in hot temps?

    If your meter is off, that g4 is never going to work.

    And no, it's not really normal from what we've seen, for us.
     
  10. DavidN

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    We've been using the G4 for 7 months and experienced what you are experiencing with one, maybe two, sensors. Someone asked about meds? You seem to be doing everything correctly. Your G4 troubles are puzzling to me.
     
  11. momof3sons

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    When we have an issue, we do three calibrations in a row five minutes apart. Dexcom suggested this and it works pretty well.
     
  12. swellman

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    I just wanted to throw out in addition we have had a few rare sensors that just never did calibrate correctly. If it's not tracking after 2 days I call it in. It happens every once in a while.
     
    Last edited: Sep 18, 2013
  13. Beach bum

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    We've only seen it happen twice and we only let it go 2 days then swapped them out. While it's not a normal occurrence for us, it has happened...and I wasn't happy:(
     
  14. ChaosRules

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    No. He only sometimes takes ibuprofen (not tylenol!), and nothing else besides insulin.
     
  15. ChaosRules

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    OK, all that is good to know. He wasn't calibrating all those times - never when it was rising or falling, even with just one arrow. He'd wait until the G4 said it leveled off, then test again and calibrate if it was more than 10% off.

    I guess we were hoping to be able to use the G4 for low and high alarms, which is hard to do when it cries wolf so often.
     
  16. ChaosRules

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    We tried two different meters, to be sure it wasn't the meter. They were within one point of each other! Which is weirdly close, but it told us that probably the meter was working fine.

    Good suggestion, though!
     
  17. ChaosRules

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    Hmmm. Hadn't heard that. We will definitely try it!

    When I called in to Dexcom, all I got told was that we were doing everything right, and everything seemed to be fine. Our expectations are too high, is all she said.

    Like I've seen others post, I was told that anything within 20% is considered accurate, and it is expected that the G4 can be wildly inaccurate 28% of the time. Oh, and you can't count the first 24 hours after a new sensor is started, so that day is a wash.
     
  18. ChaosRules

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    What happens when you call it in? Do you remove the sensor at that point, or do you ride out the week and hope it gets better?
     
  19. swellman

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    I just call it in and they tell me to swap it out and the send a new one. It just happened a week back. That sensor was a month from expiry so it might have been getting old - their is an enzyme in or on the wire.
     
  20. MomofSweetOne

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    I was told this and was very harsh on an evaluation I filled out afterwards. The company wrote me an email to follow up that I still need to respond to. I wonder if we got the same person & if we should be asking names when this occurs. If the sensors are allowed to be wildly inaccurate, then they'll be out of business in short order. Fortunately, those sensors are the exception rather than the rule.

    I find I have very little patience with people that are merely making a salary off diabetes products and are clueless about the stresses and dangers of low BGs as I'm being reassured that it is fine their product is reading 220 points off. Ummm....my kid could be in grave danger with that difference.

    Thankfully only the one Dexcom call has been like that. Medtronic seemed to blame the parents' tape job every time. I resented being told I hadn't taped carefully by individuals who had 3 whole days of experience wearing the sensor and whose pancreas self-manages so they never saw the variations and need for accuracy, nor did they pay for the sensors and have a vested interest in making sure they were taped correctly.
     
    Last edited: Sep 20, 2013

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