Each day that it is used, the CGMS System Gold must be calibrated, or compared against a known standard, four times. In this case, the standard is the user’s blood glucose meter, so at least four conventional blood glucose checks, preferably spaced fairly evenly over a 24-hour period, must be done daily and the results entered into the system monitor. (Of course, as many other checks as are necessary to maintain blood glucose control during this time should also be performed.) Blood samples from fingertips must be used for calibration because the device is not approved for calibration with blood samples from alternate sites such as arms or legs. Because blood glucose meter results are being used as the standard, it’s important that they be as accurate as possible. For this reason, it’s a good idea for CGMS System Gold users to review their blood glucose monitoring technique and meter accuracy with a health-care provider before getting started with continuous monitoring.
In addition to entering at least four daily blood glucose monitoring results, the user can (and should) also enter mealtimes, insulin (or other medicine) dose times, and exercise times. These data are stored in the system’s memory and are ultimately integrated into the analysis done at the end of the one- to three-day period. Since the system cannot store more detailed information such as what kinds of foods have been consumed or the type or intensity of exercises undertaken, keeping a daily logbook is recommended.
Because the system is not waterproof, it must be covered with a special shower pack during showers. In addition, insulin should not be administered near the sensor insertion site, and a health-care provider should be alerted if inflammation, infection, or bleeding develops at the site.
After the CGMS System Gold has been worn for the desired period of time, the sensor should be removed, the monitor turned off, and the system returned to the physician’s office. The physician can then upload the data onto a computer via a device known as the Com-Station. Special software designed for use with the CGMS System Gold organizes and presents the information in the form of pie charts and graphs. (Click here for a sample chart.)
The next generation
The CGMS System Gold monitor must be brought to a health-care provider’s office to transfer its data to a computer and analyze it. Another continuous glucose monitoring tool recently released by Medtronic MiniMed, the Guardian Continuous Glucose Monitoring System, allows the user to do that at home. This device consists of a subcutaneous sensor, a transmitter attached to the sensor with a cable, and a monitor that receives glucose readings from the transmitter via radio waves. Like the CGMS System Gold, the Guardian can be worn for up to three days at a time and must be calibrated with periodic conventional blood glucose checks. The Guardian’s monitor can also be set to sound an alarm if glucose levels are rapidly falling or rising out of range. Although glucose levels are not visible on the monitor itself, a docking station and software allow the user to upload and analyze results on a personal computer. Continuous glucose monitoring systems that show real-time glucose levels are in development by several companies.
Filling in the blanks
If you’d like to use the CGMS System Gold to evaluate your diabetes control, speak with your health-care provider. He may have or be willing to obtain a system, or he may be able to refer you to someone familiar with the device. (You can also contact Medtronic MiniMed at  MINIMED [646-4633] for assistance with locating a provider in your area.) Additionally, although continuous glucose monitoring with the CGMS System Gold is covered by Medicare and most private insurance companies, it is a good idea to speak to your insurance company ahead of time to find out whether your plan will pay for it.