The Libre accuracy report was published earlier this month and I’ve at last found a copy of it on line. And here are the highlights, and they’re pretty good! And all just after a post on The Triangle of Diabetes Care, an Abbott sponsored care approach!
The key points to take from it are:
The study contained 72 Type 1 and Type 2 patients
Overall MARD was 11.4%
Mean time lag of the sensor was 4.5 mins, +/- 4.8 mins
Sensor accuracy was not affected by factors such as BMI, age, diabetes type, Hba1C, clinical site or insulin administration
During the study, accuracy was found to be maintained over 14 days
The Consensus and Clarke Error Grid looks like this:
On the left the Consensus Error Grid shows 99.7% of all readings in Zones A & B and the Clarke grid on the right shows 99.0%.
The sensor results were shown to be within 20% of the blood glucose reference (whether capillary on the Libre reader or venous) 86.2% and 82.8% of the time respectively.
The distribution in MARD is shown in the histogram below:
Suffice to say that this study has given Abbott a lot of data that they can now put in front of groups like the NHS and NICE plus Insurance companies to represent that this is an accurate and usable alternative to SMBG. This is why they have recently scaled up production and provides them with a huge profit opportunity.
In tandem with the Triangle of Diabetes Care work, this is now being targeted at both Type 1 and Type 2 diabetics as a great way to help more people to meet Hba1C targets. The report references the RCTs that show CGM sensor wear reducing Hba1Cs as well. All in all, I’d say it paints a very positive picture of the outcome of the trials, and I’m sure it is what Abbott were expecting.
For a PDF copy of the report, please follow this link.
For a version that contains links to the images, use this one.
A brief description of the Clarke Error Grid. The Consensus Error Grid is an updated version of this.
The Clarke Error Grid Analysis (EGA) was developed in 1987 to quantify clinical accuracy of patient estimates of their current blood glucose as compared to the blood glucose value obtained in their meter. It was then used to quantify the clinical accuracy of blood glucose estimates generated by meters as compared to a reference value. A description of the EGA appeared in Diabetes Care in 1987. Eventually, the EGA became accepted as one of the “gold standards” for determining the accuracy of blood glucose meters.
The grid breaks down a scatterplot of a reference glucose meter and an evaluated glucose meter into five regions:
Region A are those values within 20% of the reference sensor,
Region B contains points that are outside of 20% but would not lead to inappropriate treatment,
Region C are those points leading to unnecessary treatment,
Region D are those points indicating a potentially dangerous failure to detect hypoglycemia or hyperglycemia, and
Region E are those points that would confuse treatment of hypoglycemia for hyperglycemia and vice versa
Remember the plot of the Harrison Ford movie “The Fugitive” where fake samples were substituted for real samples to gain positive results? There is NO doubt in my mind that the testers of Abbot’s Libre likewise substituted fake results. Ask any (past) user of the Libre, look at the online comments to include YouTube videos from users. The Libre is DANGEROUS as the results vary so widely, so inaccurately, they can cause a DEATH!
I have been using the Libre Freestyle for 2 days, checking it 4-6 times a day against my two regular monitors(Livongo and OneTouch Ultra), and so far only one reading has been within 30 points either direction of the other 2 monitors. Most of the time it is around 40 points off, but it has been off by more than 50 points several times.
Hopefully it will become more accurate. As of now, I would not depend on thus as my only source of measurement.
I echo those who unequivocally state that their readings with the FreeStyle Libre have been very inaccurate. My experience has been that not only I cannot trust the Libre to be accurate within tolerable limitations but that my range of results with each sensor has been significantly different than my previously used sensors. For those like myself who are on “self-pay” using the FreeStyle Libre has been a very expensive mistake.