Diabetes Developments

The Most Accurate Continuous Monitor

For years many people that I know have been waiting to use Abbott’s FreeStyle Navigator continuous glucose monitor. As long ago as February 2005 I wrote in Diabetes Health magazine that, “The FreeStyle Navigator Continuous Glucose Monitor is coming.”

Preliminary studies had indicated that it might raise the accuracy bar. And now, according to a study to be published in this month’s issue of Diabetes Care it really will be more accurate than the competition. The Navigator will be more accurate where it counts than the three other monitors that the study evaluated.

Full disclosure: I have tested and written about one of these monitors, the Guardian REAL-Time, here. I also own 150 shares of a company, DexCom, that makes another. I unwisely purchased 150 shares of DexCom at $14.832 on January 18, 2006. It’s now selling for $7.89 per share. So, if I had a conflict of interest, I certainly wouldn’t be writing this article.

The accuracy comparison included a fourth continuous monitor, A. Menarini’s Glucoday S. While this Italian monitor is available in Europe, the Food and Drug Administration has not approved it for sale in the United States.

The comparison, however, did not reach as far as Israel where OrSense offers its NBM-200G continuous non-invasive monitoring system. The omission is strange enough that I wrote the lead author.

The lead author of the new study, Boris Kovatchev, PhD, of the University of Virginia, replied today that their “goal was not to make a comprehensive review of all available continuous glucose monitors.” Dr. Kovatchev is one of the biggest names in academic testing of our blood glucose monitors. It was Dr. Kovatchev who developed the new low, high, and combined blood glucose indices incorporated into the Accu-Chek Smart Pix Device Reader that I wrote about here last year.

Another author, William Clarke, MD, also of the University of Virginia is famous for having developed the Clarke Error Grid, which most people use to evaluate meter accuracy. So when two big names in meter testing team up, it’s important to sit up and listen. I did, even if the company that I own stock in did worse in accuracy where it counts.

Where it counts is in hypoglycemia. When our blood glucose levels go too low — what we familiarly call “hypos” — getting the correct amount of insulin into our system becomes even more crucial. One study of 14 adults with type 1 diabetes and another of 20, showed that the numerical accuracy of DexCom’s original three-day STS monitor was about 30 percent less in both the hypo and normal ranges. They did not test the newer DexCom Seven, acknowledging that, “Recent data collected with the new 7-day DexCom sensor showed improved accuracy of the device…”

The study concluded that numerical accuracy of Guardian, Navigator, and Glucoday was comparable, “With an advantage to the Navigator in hypoglycemia.” The clinical accuracy of the four sensors was similar in euglycemia (the technical term for normal levels). In the hypoglycemic range the Navigator and Glucoday were better.

The FDA approved the Navigator for sale early this year, several years after Abbott’s original submission. The Abbott press release issued in March says that it “will be available in the second quarter of 2008.” If your doctor prescribes it, this means that you can get one this month — assuming that Abbott is a lot quicker to get the Navigator to market than the FDA was to approve it.

This article is based on an earlier version of my article published by HealthCentral.

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  • Reply Annamaria Basile December 23, 2009 at 2:31 am

    Dear David,

    please note that saying that “the Food and Drug Administration has not approved GlucoDay S for sale in the United States” is not correct because A.Menarini Diagnostics has never applied for FDA clearance.

    Annamaria Basile

    • Reply David Mendosa December 23, 2009 at 8:35 am

      Dear Annamaria,

      I appreciate your reading my articles and writing. But actually what I wrote is correct in terms of American English. Please note that I did not write that the FDA disapproved the GlucoDay S.

      By the way, many people would like to know if and when you plan to submit the GlucoDay S to the FDA. Do you have any plans?

      Best regards,


  • Reply David Mendosa October 23, 2008 at 12:29 pm

    Dear Bob,

    Thank you. I am sorry to hear that.

    Best regards,


  • Reply Bob Schlegel October 23, 2008 at 8:12 am


    I am the one who brought you up to date on Tom Clemens some 18 months ago. As you may remember you contacted Tom about the serious medical condition she was suffering with. Effie died of ovarian cancer about 3 months ago. Thought you might like to know.

    I speak to Tom every now and then. Tom worked for me when I was the President of Ames Company, a.k.a. Bayer Diagnostics.


  • Reply David Mendosa October 20, 2008 at 5:30 pm

    Dear Bob,

    The company’s website provides this contact information:

    5 Golda Meir St,
    Weizmann Science Park,
    P.O.Box 4052,
    Nes Ziona 74140,

    Tel: 972-8-9465142
    Fax: 972-8-9465502
    Email: orsense@orsense.com


  • Reply Robert P. Schlegel October 20, 2008 at 1:05 pm

    Is the Israeli company OrSense still operating? If yes, how do I contact OrSense.


    Bob Schlegel

  • Reply David Mendosa August 24, 2008 at 12:38 pm

    Dear Evon,

    Excellent question! I’m sorry, but I have had the same experience with Orsense.


  • Reply evon August 24, 2008 at 12:20 pm

    Why do you think the Orsense NBM-200G is available in eurpoe? and if so WHERE? I can’t find it, nor do I get any response from Orsense.

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