Head-to-Head Comparison of Professional vs Personal CGM Systems in T1D

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Researchers note that it is worrisome that both CGM systems tend to overestimate glycemia in cases of hypoglycemia, as patients may make incorrect treatment decisions based on inaccurate readings.
Researchers note that it is worrisome that both CGM systems tend to overestimate glycemia in cases of hypoglycemia, as patients may make incorrect treatment decisions based on inaccurate readings.

Professional and personal continuous glucose monitoring (CGM) systems exhibit similar accuracy in both inpatient and home settings, with both having lower sensor performance during hypoglycemic episodes, according to study results published in Diabetes, Obesity and Metabolism.

Researchers compared the precision of professional and personal CGM systems while being used in parallel in patients with type 1 diabetes. Both monitors were affixed to the subcutaneous adipose tissue of patients' thighs for a 24-hour inpatient phase during which patients received standard meals followed by increased bolus insulin doses to induce mild hypoglycemia. The study continued for a subsequent 5-day home phase during which typical activities and diabetes care were performed, capillary glucose measurements were taken at least 7 times, and all meals and insulin doses were recorded in a diary.

Of the 10 adults included in this study, 6 were women, the average age was 30.5 years, the average body mass index was 24.4 kg/m2, the average HbA1c was 53.3 mmol/mol, and the mean daily insulin dose was 39 U. During the inpatient phase, the professional CGM system met International Organization for Standardization (ISO) criteria for blood glucose monitoring systems by 58.4% overall compared with the personal CGM system which met ISO criteria by 57.8% overall. During the home phase, the professional CGM system met ISO criteria by 66.5% overall compared with the personal CGM system which met ISO criteria by 65.3% overall. There were no significant differences in performance between CGM systems for either phase of the study or for time of day.

As expected, the glucose monitors were less accurate during periods of hypoglycemia. The professional CGM system overestimated hypoglycemic glucose readings 57.7% of the time and underestimated hypoglycemic glucose readings 38.5% of the time. The personal CGM system overestimated hypoglycemic glucose readings 64.3% of the time and underestimated hypoglycemic glucose readings 35.7% of the time. There were no significant differences between CGM systems for hypoglycemic measurements, but the researchers noted that it was “especially worrisome that both CGM systems [tended] to overestimate [glycemia] when compared [with] capillary glucose.”

Overall, the professional and personal CGM system performed similarly at night and during the day, both in the inpatient and home settings, and had reduced sensor accuracy during hypoglycemic episodes. The researchers concluded that “it is worthwhile knowing that especially during [hypoglycemia,] CGM-derived data need to be questioned and might require confirmation by capillary [blood glucose] measurements. This is also true for [professional] CGM when used as diagnostic tool, both in routine care and in outcome studies where duration and frequency of [hypoglycemia] needs to be interpreted with caution.”

Multiple authors declared associations with the pharmaceutical industry. Please see the reference for a full list of authors' disclosures.

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Reference

Moser O, Pandis M, Aberer F, et al. A head-to-head comparison of personal and professional continuous glucose monitoring systems in people with type 1 diabetes: hypoglycaemia remains the weak spot [published online November 28, 2018]. Diabetes Obes Metab. doi:10.1111/dom.13598

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