https://onlinelibrary.wiley.com/doi/full/10.1111/jvim.16122
Accuracy of a flash glucose monitoring system in cats and determination of the time lag between blood glucose and interstitial glucose concentrations
Conclusions and Clinical Importance
The FGMS did not fulfill ISO requirements but is sufficiently accurate for glucose monitoring in cats, while considering the lag between IG and BG during periods of rapid changes in BG.
The details are important.
Always look to the discussion section vs just the conclusion statement 
as the conclusion statement typically speaks to the hypothesis, yet doesn’t provide details that are important. (Note: this is similar to the Cabergoline Article. While at first glance, & if one just looks at the conclusion, people jump to think the author is stating it doesn’t work, but if one reads the discussion section that is not the case at all
)
The details......Re: those ISO requirements
“Only 42.2% of all data points included in our study were within the limits of analytical accuracy based on ISO 15197:2013 requirements. In contrast, a previous study using the hexokinase method as a reference found better results, with 67.7% of FGMS measurements within the ISO 15197:2013 requirements.
16 However, Parkes EGA showed good clinical accuracy with 100% of readings in zone A and B. The ISO 15197:2013 standards require comparison of BG meter measurements with the results of a standard reference method.
However, these standards are designed for comparisons of results from a single compartment, typically the blood, and comparisons between 2 different compartments (blood and interstitial fluid) may be inappropriate because of the physiological differences between these compartments. In the absence of established standard criteria for evaluation of the accuracy of glucose measurements in the interstitial fluid, the ISO criteria for the evaluation of PBGMs provide a relevant substitute to identify devices that are as close as possible to meeting accuracy criteria and that are not dangerous for the animal's health.”
“With this caveat, the FGMS can be considered acceptable for clinical use, despite analytical accuracy requirements not being met.”
“In conclusion, the FGMS provides clinically accurate measurements in the euglycemic and hyperglycemic ranges.”
My cat is actually treated by one of the authors of this publication & yes, without question, he is an advocate of using the CGM. It provides dynamic information that is just not possible to obtain with BG measurements alone.
I will share with you, from personal experience, that the 2nd generation Libre is night and day in terms of accuracy even in the lower ranges of glucose
. It is the same with humans.The publication was done using the 1st generation & despite it being less accurate than the 2nd generation, as stated in the publication, it “provided clinically accurate measurements”.
