What follows is DexCom's response to Zachariah Kramer's letter to Diabetes Health cautioning against unrealistic expectations about CGMS.

DexCom’s Response:

June, 2008

We applaud Mr. Kramer’s decision to pro-actively manage his diabetes with a pump and a CGM system and we agree with his assessment that realistic expectations need to be set prior to going on a CGM system to help ensure successful incorporation into their diabetes management.  

Mr. Kramer refers to the lag time between capillary and interstitial glucose readings as one of the main issues in using today’s CGM systems.   This is correct for “traditional”interstitial fluid (ISF), which can have as much as a 30-minute time lag.  However, when a sensor is inserted into the body a small “wound” is created by the introducer needle and the fluid in the area immediately surrounding the Sensor is called serous fluid.  The body goes to work at this localized area and starts its ‘healing process’ – it does so by increasing the oxygen and glucose in the serous fluid to fuel the healing process.  This is true for all of the current sensor systems, but, the size of the introducer needle and Sensor can impact how quickly the healing response is started.  In addition, it should be noted that some devices introduce “smoothing” of the raw signal as measured by the glucose sensor, and this “smoothing” can introduce mechanical lag time as well.  

In reference to the DexCom Seven System, the average lag time is 5 minutes and is not impacted by the rate of change of glucose thus providing two key benefits to the user:
1.)    Minimal lag times allow the Seven system to be more accurate particularly in the low glucose region.  
2.)    Sensor stability throughout rates of glucose change give the patient the ability to calibrate whenever they need to without having to wait for their glucose to return to a steady state.

Mr. Kramer is correct:
-    CGMs do take work while you are getting comfortable with the new technology.  And it’s important not to get discouraged, before benefits are experienced.  Just as a new cell phone takes a while to get used to new features, after a little time the System will become second nature.
-    CGMs do not replace finger sticks.  Each system relies on finger stick measurements for calibration (typically 2/day).  While initially you may find yourself doing more finger stick measurements, many users end up reducing the overall number of finger stick measurements to calibrate and to confirm high or low BG readings before treatment or dosing.
-    Reimbursement of CGM Systems is slow – but it is happening.  Just like any new technology, the adoption of insurance companies takes time.  We are encouraged to see how rapidly insurance companies are actively conducting reviews of the technology.  As many key opinion leaders stated at the recent ADA Scientific Sessions, it is only a matter of time until CGM is the standard-of-care in diabetes management.  You can help in this process by submitting claims to your insurance companies and by following the formal appeals process.  This helps to build awareness within the insurers, of the usage and need for coverage of these devices.

Today’s CGM Systems are not perfect, but they do provide the very important and useful insight into where and how fast your glucose is going thereby giving you the ability to actively make a change to help you to ‘stay between the lines’.