Benefits of Freestyle Libre (CGM)
- Libre prevents many Fingerpricks
You’re familiar with the ease of knowing the current glucose level at a glance if you’ve ever used a Continuous Glucose Monitor (CGM). Flash Glucose Monitoring provides the same relief: glucose controls are quick, easy, and painless; all that needs to be done is to place the reader over the sensor to “scan” it, wait 1 second for processing, and on the screen, your current glucose reading pops up. Flash Monitoring removes the need to wash hands, getting and putting the strip in, wait for the meter to be available, administer the blood drop, and then waiting 4-6 seconds for the meter to analyze the sample and show the result for most of the glucose checks performed in a day. Moreover, with a fingerstick meter scan, you do not need to calibrate the system, as you do with CGM systems. There is no way of entering an external number with Flash Glucose Monitoring, and calibration is not feasible. There are cases where a fingerstick BG check is still suggested, but the simple truth is that more fingerstick checks are replaced by Flash than any other form of glucose-checking.
- The Back Data
Besides telling you the latest glucose reading when you scan the sensor, a graph of the sugar readings for the past 8 hours is also shown by the reader, whether or not you previously examined the sensor during that time. This is because glucose is continuously measured by the sensor, automatically storing the reading every 15 minutes*. When you check the sensor with the reader, the Data then becomes visible to you.
Secondly, you don’t have to worry about it; the sensor takes the readings and stores them 24/7; you get a complete, continuous data set as long as you check at least once every 8 hours without remembering to search periodically during that time.
Also, this ongoing data collection ensures that in terms of your sugar levels, you not only know where you are, you also know where you’ve been and the path that got you there.
In reality, this back-data enables for in-the-moment pattern data. That is, when you see a 5.5 mmol/L reading, you can ask, “Does my glucose remain steady at 5.5?” Is it going to decrease over the next few minutes? Or is it going to rise? These various patterns in glucose will lead you to keep up the good habits. If there is a drop in glucose, you can decide what to eat to avoid a slip. You may want to stop eating if glucose rises and check back in half an hour to make sure it hasn’t skyrocketed. You can relax if the glucose is steady, knowing you don’t need to take the necessary steps right now. In each case, the trend data made possible by the back-data impacts your response.
In case you’re wondering, in terms of back data, the device stores the singular reading that happens at the 15-minute stage, not the sum of all the readings during that period. However, all the information from the previous 15 minutes is used by the device for trend details. And the device shows the actual reading for the present sugar reading when you check, in real-time, not the measurement at the start of the current 15-minute period.
- The Accuracy
When it comes to Flash Glucose Monitoring, precision is a bit of a complex problem. How do we test accuracy? What external indicators do we use to judge this, to begin with? CGM accuracy testing studies also use a lab analyzer to compare and calculate how well a series of sensor readings match these BG values. Reviews from the United States supporting its accuracy have been released, including one funded by Abbott Diabetes Care (Freestyle Libre manufacturers), which shows that ‘interstitial glucose measurements with the FreeStyle Libre method are accurate compared to capillary BG reference values, with reliability remaining stable over 14 days of wear.’
“The nitty-gritty details of that study: “The accuracy of the findings was demonstrated against capillary BG reference values, with 86.7 percent of sensor results within Consensus Error Grid Zone A” (Zone A is described as no impact on clinical action”).”
Translation: compared with reference values for capillary BG, i.e., About 86 percent of the Libre test data were close enough to the meter readings so that the patient would not have gone new activities based on the Libre results than they would have to occur as a result on the meter results, Fingerstick results using a blood glucose meter. Also, about 11 percent was the average difference between Libre readings and meter readings.
What does that imply? Does this mean that the CGM was more concise than the meter, or was it more accurate than the meter? We have no real means of knowing as sensors can also be “out” by up to 15% and still be considered relevant by current standards. Furthermore, we must bear in mind that the two readings calculate different factors: the device senses the sugar in the interstitial fluid, while the lab measures the sugar in the body. These factors are estimated at some point in time.
And what about any Lag Time?
First, glucose shows up in the blood. It travels through the body through the blood and out through the surrounding tissue and organs. It takes time for this tissue movement process to occur, causing a lag between blood glucose and glucose in the interstitial fluid where the sensor measures glucose. This lag time happens when glucose increases (such as when we eat or when the liver releases stored glucose) and when it decreases (when insulin is active or when glucose is drawn from the blood to feed the muscles due to exercise).
The sensor can read a lower blood sugar level than the actual blood glucose level (similar to the glucose level in the blood 5-10 minutes ago) as the glucose level increases.
The sensor can read a higher blood sugar than the current glucose levels (similar to the level of sugar in the blood 5-10 minutes ago) when the glucose level decreases.
So if you feel the symptoms are low, but the sensor says the glucose is in range, it’s prudent to use a blood glucose meter to double-check.