Accuracy of Navigator in Children with T1

[Ellen]

From the January 2007 Diabetes Care

Emerging Treatments and Technologies
Original Article

The Accuracy of the FreeStyle Navigator Continuous Glucose Monitoring System in Children With Type 1 Diabetes

Darrell M. Wilson, MD, Roy W. Beck, MD, PHD, William V. Tamborlane, MD, Mariya J. Dontchev, MPH, Craig Kollman, PHD, Peter Chase, MD, Larry A. Fox, MD, Katrina J. Ruedy, MSPH, Eva Tsalikian, MD, Stuart A. Weinzimer, MD and the DirecNet Study Group

From the DirecNet Coordinating Center, Jaeb Center for Health Research, Tampa, Florida
Address correspondence and reprint requests to Darrell M. Wilson, MD, DirecNet Coordinating Center, Jaeb Center for Health Research, 15310 Amberly Dr., Suite 350, Tampa, FL 33647. E-mail: direcnet@jaeb.org (direcnet@jaeb.org)
OBJECTIVE—To evaluate the accuracy and precision of the FreeStyle Navigator continuous glucose monitoring system in children with type 1 diabetes.
RESEARCH DESIGN AND METHODS—In 30 children with type 1 diabetes (mean age 11.2 ± 4.1 years), the Navigator glucose values were compared with reference serum glucose values of blood samples obtained in an inpatient clinical research center and measured in a central laboratory using a hexokinase enzymatic method and in an outpatient setting with a FreeStyle meter. Median absolute difference (AD) and median relative absolute difference (RAD) were computed for sensor-reference and sensor-sensor pairs.
RESULTS—The median AD and RAD were 17 mg/dl and 12%, respectively, for 1,811 inpatient sensor-reference pairs and 20 mg/dl and 14%, respectively, for 8,639 outpatient pairs. The median RAD between two simultaneous Navigator measurements (n = 1,971) was 13%. Ninety-one percent of sensors in the inpatient setting and 81% of sensors in the outpatient setting had a median RAD http://care.diabetesjournals.org/math/le.gif20%.
CONCLUSIONS—The Navigator’s accuracy does not yet approach the accuracy of current-generation home glucose meters, but it is sufficient to believe that the device has the potential to be an important adjunct to treatment of youth with type 1 diabetes.
Abbreviations: AD, absolute difference • CGMS, continuous glucose monitoring system • CRC, clinical research center • ISO, International Organisation for Standardization • RAD, relative absolute difference

[BrendaK]

How does this compare with Minimed's Real Time sensor?

[Jeff]

Based on this and previously published studies, the Navigator has better accuracy in the hypoglycemic range than other continuous sensors.

[EmmasMom]

This is the accuracy info on the real-time sensor.

MARE: 16.59% - 24.84%%
Clark Error Grid - 96% in A+B and 61.7% in A
MARD (Mean) - 17.32%
MARD (Median) - 12%

MARD= Mean Absolute Relative Difference (Percentage)


It's difficult to figure out how the whole picture on the Navigator results compare to MM's because they're split into inpatient and outpatient groups. It looks like the Median Absolute relative difference on most patients in both groups was >20%. With in patients seeing slighty better results than out patients.
I honestly don't see a huge difference between the two.

When two sensors were worn simultaneously the Navigator accuracy averaged 13% and MM's 17%. So a little bit better, but it would only translate to a few points difference on your readings.

I've been talking to a mom on another forum who's daughter had been on the Navigator for a year, (she's involved in the trial), she says the accuracy has been very good. But it's really almost the same that we're getting w/ the RT. I'm sure as with everything else... YRMV!

[thebestnest5]

Although, I would like to see the Navigator have results like that of a fingerstick on a blood glucose meter, I am encouraged by (possbily) having more accurate results in the hypo range. I am more concerned about the immediate dangers of a hypo.

I think the 90 degree set is a HUGE plus, IMO, over the angled sets now available in other CGMS.

If the waterproof capabilities that are rumored are true than this will be yet another advantage of the Navigator.

I won't get hung up on brand loyalty...my loyalty is to my daughter...I'm looking for the most accurate, most comfortable, most convenient CGMS.:cwds:

[EmmasMom]

Although, I would like to see the Navigator have results like that of a fingerstick on a blood glucose meter, I am encouraged by (possibly) having more accurate results in the hypo range. I am more concerned about the immediate dangers of a hypo.

I think the 90 degree set is a HUGE plus, IMO, over the angled sets now available in other CGMS.

If the waterproof capabilities that are rumored are true than this will be yet another advantage of the Navigator.

I won't get hung up on brand loyalty...my loyalty is to my daughter...I'm looking for the most accurate, most comfortable, most convenient CGMS.:cwds:

I agree completely! The sensor and transmitter on the current systems need to be improved, (and hopefully they will be soon). The real-time sensor is waterproof, but it still doesn't like sitting in very warm water, which may be an issue for all of the them. I hate putting an angled set in Emma and I can't wait for something smaller and more user friendly. The bottom line though, is that we've got an amazing tool that's helping us right now, and the pros far outweigh the cons!

Hopefully the market will be so hot for these things that competition will be fierce between companies and everyone will have a fabulous product at some point!!!
I feel like we chose the best thing for us for right now, but I would happily change to any company that can offer me a better product in the future!!
I was just fantasizing today about the ultimate pump. One that had the new software of the cozmo, the smaller basals of the animas, the integrated CGMS and meter of the MM, and the cordlessness of the omnipod, (only smaller). And the CGMS would, of course, be tiny and incredibly accurate. ;) Ahhh! Perfection! Of course a cure would be even better!!

[thebestnest5]

Me too!! :D I look at the new Ipods and I think....oooh, wouldn't it be great to have a pump/CGMS that size?? Or, even a fabulous insulin that creates euglycemia ...and a CURE....well that would truly be the best.

[Adinsmom]

I was just fantasizing today about the ultimate pump. One that had the new software of the cozmo, the smaller basals of the animas, the integrated CGMS and meter of the MM, and the cordlessness of the omnipod, (only smaller). And the CGMS would, of course, be tiny and incredibly accurate. ;) Ahhh! Perfection! Of course a cure would be even better!!

Exactly! :cool: I hope somebody in one of the companies is listening.

[DotConnector]

I posted the message below in another thread, but I wanted to comment here because I also have a 6 year-old with type one and tried to get her in on the study I am participating in. No luck.

Anxious for this technology for her. We both have minimed pumps, but I want smaller transmitters and better accuracy--Like the Navigator I'm in trial with now.

Oh! I wear this in the shower no problem and is good for up to three feet deep in pool.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I have been part of the Abbott Diabetes Care trial for their Freestyle Navigator Continuous Glucose Monitor for about 30 days. I gotta tell you, I LOVE this thing! I am most impressed with the accuracy, but there are a few cons, that I outline in my relatively new blog at http://diabetesselfcare.blogspot.com/.

I decided that this was WAY too cool to keep to myself, so I have posted details of my experience so far and have included pictures as well.

I only wish I got to keep the CGM when the trial was over! I'd love to hear from other folks using CGM's. This is the best thing since insulin!

Wendy