I posted this message on another section of the forum here, but I am posting it here again to reach more people that might not see it otherwise. I had the problems with the accuracy of the new 505 software, as others have mentioned here and in the other thread. I did figure out ultimately that it was related to my doctor prescribing me the wrong strips for my standard glucose meter. Here it is:
I was having issues similar to what people on this group have mentioned. I think I figured out what is going on with the inaccurate numbers with Dexcom's new 505 software version. I discovered that it is not a problem with the Dexcom software in my case.
I went through Dexcom's tech support channels, and ultimately ended up on the phone with one of their supervisors. Since the update, I was having a bunch of issues. False low alarms (my real BG was 154 mg/dl, Dexcom was reading 48 mg/dl), and very inaccurate numbers otherwise. Dexcom did replace that sensor for me, but it turns out that it was not a bad sensor, like I thought. I started having to test more often, because I really didn't trust the numbers I was getting with the Dexcom G4. It would have gotten expensive very quickly, as I was having to test as many as 8 times per day.
The supervisor at Dexcom thought that it may be an issue with my blood tester, and recommended that I get a new blood tester to check the numbers against. I didn't have enough money to buy a replacement blood tester, so I contacted my blood tester manufacturer (Abbott Labs Freestyle, InsuLinx). They sent me out control solution to verify that the tester is working properly, and the control solution showed that the tester was within the specified requirements.
When I got in touch with Freestyle's tech support, they had me read off the lot number that I was using to their support representative. I came to find out that I was using the test strips that DO require coding before using them. In this case, the yellow label bottle that I was using said Code 16 on it. The Freestyle InsuLinx monitor DOES NOT require coding whatsoever, and the label on the bottle is WHITE for the InsuLinx strips. The bad thing is that Abbott labs makes 3 types of test strips, and only the InsuLinx blood test strips are compatible with my tester-however all 3 types of test strips LOOK identical and will function in the InsuLinx tester. The problem was that I was using the Freestyle test strips (wrong strips) on my Freestyle InsuLinx monitor.
I went down to the pharmacy and exchanged the unopened box of strips that I had for the InsuLinx test strips. I then started using the new strips to calibrate the Dexcom G4. Since I have been using the new strips, my blood sugar on the InsuLinx tester has been within 8 mg/dl difference from the Dexcom G4. 8 mg/dl difference is satisfactory performance to me.
The problem was caused because the doctor that I go to had prescribed me the wrong test strips! For all those that are having inaccuracies with the new 505 software, please call your manufacturer of your tester and verify that you are using the correct test strips.
I have contacted Dexcom's supervisor, and Dexcom is now aware of this issue. I really wish that test strip manufacturers would make physically different shaped or colored test strips, if multiple varieties that are NOT compatible will work on the same tester!
I hope this helps people who have had the same issues as I was having with the 505 software.