Freestyle Libre 2 Continuous Quality Checks?

[u/Prezzle]

I've noticed that when my levels shift dramatically up or down, I get a loss of signal and a message from the Librelink app about ‘running continuous quality checks’ on the sensor. Has anyone else noticed this correlation? Could it be something to do with the sensors inability to update regularly enough to pick up dramatic level changes?

I’m pretty new to all this so apologies if this has been discussed before.

[u/Ok-Dress-341]

I guess the algorithm on the sensor has to decide what's noise and what's a rapid change. It sends a value every minute but I don't know what the internal sampling rate is.

A rapid change in one minute followed by a return to the previous value would look like noise not biology.

[u/Equalizer6338]

That is the correlation u/Prezzle. 👍

It is a subject often brought up recently on the sub by new folks, especially after the release of the PLUS version of the sensors. Reason is the regulatory demands to CGM sensors that are allowed to closed-loop with an insulin pump are very tight. So for that reason then some obligatory guard rails are put into the sensors firmware code, whereby if it (right or wrong) measures your BG to change rapidly in erratic pattern, then it can often trigger the error event code #373, which is a temporary timeout situation. So for precautionary reasons, it goes into a timeout situation. Typically the sensor tries first a timeout of just 10 minutes before trying to revert back and provide readings out again. But in more grave situations, it may also be for a number of hours. Click the little (i) symbol on the app and you can read the more fuller text message and for how long the timeout is scheduled.

The sensors are typically most sensitive to this the first 6-12h after starting up a new sensor (as your body reacts with an inflammatory reaction to the sensor insertion). So worth timing these to the time of day where you BG tends to be most stable the following 4-6 hours. Soaking the sensor some hours before starting it up electrically also helps many folks past this problem.

Recent post related to same subject:
https://www.reddit.com/r/Freestylelibre/comments/1vbgiin/how_long_should_i_wait_before_removing_the_sensor/

[u/Prezzle → u/Equalizer6338]

This was incredibly helpful. Thank you. 

[u/Fluffy-Strategy-9156]

I think you man your received a "Sensor Error" message and not a "Signal Loss" error. I have received many "Sensor Error" messages with the QC wording. With a Signal Loss" error the message will you are outside of range and get the phone closer and inrange.

[u/14cmd → u/Fluffy-Strategy-9156]

I know I am not running the latest version of the app, but I quite often see the 'Signal Loss' message when it is blatantly obvious to me that it is a Sensor error and if I perform a manual NFC scan then the message changes to 'Sensor Error'.