Dexcom's G4 Platinum CGMS

A redesigned, more accurate, and sleeker system

By Adam Brown and Kelly Close, diaTribe

Although the FDA first approved personal CGM over a decade ago (Cygnus' GlucoWatch in 2001), a new device for personal use has not been approved since Dexcom's Seven Plus in 2009. Encouragingly, the FDA ended the dry spell in October by approving Dexcom's new G4 Platinum CGM system (the "G4" stands for fourth generation, since this product follows the STS, Seven, and Seven Plus). With Kelly and Adam's (many!) combined years of experience using the Seven Plus (a great product in its own right), what follows is our early take on our favorite improvements in the G4 Platinum, namely in 1) improved accuracy and reliability; 2) a sleeker receiver design; and 3) an extended transmission range.

Improved Accuracy and Reliability

Kelly and Adam's Favorites

  • Better overall accuracy, especially in hypoglycemia
  • Fewer large deviations (outliers) from blood glucose meter readings
  • Fewer question mark sensor signal errors ("???")

Based on the pivotal trials for the Dexcom G4 Platinum and the Seven Plus, the G4 Platinum CGM is nearly 20% more accurate overall and over 30% more accurate in the hypoglycemia range. In wearing the Seven Plus and G4 Platinum simultaneously, Adam found the overall accuracy improvement was actually quite noticeable, especially for hypoglycemia. While the Seven Plus would sometimes over/under read hypoglycemia (compared to a blood glucose meter) and lag behind low blood glucose values, the G4 Platinum was generally in line with meter readings in the low range — this was a big deal to both of us. One of CGM's biggest benefits is that it helps users avoid hypoglycemia (or at least minimize time spent in hypoglycemia), so this improvement in accuracy is very encouraging for patient safety.

In the past, we found that the Seven Plus also had occasional problems with outlier values — those CGM readings that deviate considerably from actual blood glucose values. For instance, one study showed that a Dexcom Seven Plus sensor chosen at random has on average 19 hours per month of large errors over 50% (e.g., a blood glucose meter reading of 100 mg/dl vs. a corresponding CGM reading of 150 mg/dl or 50 mg/dl). Through an improved sensor membrane design and better algorithms, the G4 Platinum has reduced the likelihood of these outlier values. In other words, not only is the system's average accuracy better, but the accuracy range is also narrower.

A last minor frustration with the Seven Plus was the "???" display. When that happened, no glucose data would appear, and the user could only hope the sensor came back online or prompted for a calibration. These errors sometimes lasted for quite awhile and in some cases required changing the sensor before seven days were up. While the G4 Platinum can still have these errors in theory, we have not had any so far in our experiences with multiple seven-day sensor sessions.

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Last Modified Date: June 14, 2013

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