Department of Pharmaceutical Care, University of Iowa Hospitals & Clinics, Iowa City (Dr. Schleich); Department of Family Medicine, Carver College of Medicine, University of Iowa, Iowa City (Drs. Schleich and Ray) kevin-schleich@uiowa.edu
The authors reported no potential conflict of interest relevant to this article.
There is no universally accepted standard for determining the accuracy of a CGM; however, the mean absolute relative difference (MARD) is the most common statistic referenced. MARD is calculated as the average of the absolute error between all CGM values and matched reference values that are usually obtained from SMBG.31 The lower the MARD percentage, the better the accuracy of the CGM. A MARD of ≤ 10% is considered acceptable for making therapeutic decisions.30
Package labeling for all CGMs recommends that patients have access to a fingerstick glucometer to verify CGM readings when concerns about accuracy exist. If a sensor becomes dislodged, it can malfunction or lose accuracy. Patients should not try to re-apply the sensor; instead, they should remove and discard the sensor and apply a new one. TABLE 210,14-17 compares MARD for CGMs and lists substances that might affect the accuracy of a CGM.
Patient–provider data-sharing platforms
FreeStyle Libre and Libre 2.Providers create a LibreView Practice ID at www.Libre View.com. Patient data-sharing depends on whether they are using a smart device, a reader, or both. Patients can utilize both the smart device and the reader but must upload data from the reader at regular intervals to provide a comprehensive report that will merge data from the smart device (ie, data that have been uploaded automatically) and the reader.7
Dexcom G6.Clinicians create a Dexcom CLARITY account at https://clarity.dexcom.com and add patients to a practice list or gain access to a share code generated by the patient. Patients must download the Dexcom CLARITY app to create an account; once the account is established, readings will be transmitted to the clinic automatically.15 A patient who is utilizing a nonsmart-device reader must upload data manually to their web-based CLARITY account.
Family and caregiver access
Beyond sharing CGM data with clinic staff, an important feature available with FreeStyle Libre and Dexcom systems is the ability to share data with friends and caregivers. The relevant platforms and apps are listed in TABLE 2.10,14-17
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