Lets be careful @Dennis One of the current standards for Self-Monitoring Blood Glucose Test Systems (SMBG) is
… 95% of all SMBG results in this study are within +/- 15% of the comparator results across the entire claimed measuring range of the device and that 99% of all SMBG results are within +/- 20% …
The current standards for CGMs that can be used for automated dosing are more nuanced. One standard is
… For all iCGM measurements from 70 mg/dL to 180 mg/dL, the percentage of iCGM measurements within +/-15 percent of the corresponding blood glucose value must be calculated, and the lower one-sided 95 percent confidence bound must exceed 70 percent. …
Manufactures are not required to publish MARD for SMBG. MARD is not the only metric that should be compared between CGMs. For SMBG it is easy to compare the % within 5,10,15% results in the back of the manual.
Checking SMBG with lab results is a great way to make sure your meter and current test strips are within 20% of the lab result. The comparison is only useful as a pass/fail test. A single data point doesn’t help when comparing CGM to SMBG values.