Discrepancies between current displayed and auto-logged glucose values in FreeStyle Libre 3: Implications for...

Area of Science:

• Diabetes Technology
• Endocrinology
• Biomedical Engineering

Background:

• The FreeStyle Libre 3 (FSL3) continuous glucose monitoring (CGM) system offers both auto-logged (AL) and current displayed (CUR) glucose values.
• These values are often treated as interchangeable, but potential discrepancies and their clinical significance require thorough investigation.

Purpose of the Study:

• To compare AL and CUR glucose values from the FSL3 system.
• To investigate the clinical relevance of any observed discrepancies, particularly in critical glycemic situations.

Main Methods:

• Analysis of 15-day FSL3 data from 24 participants, including in-clinic sessions with controlled glycemic excursions.
• Paired AL and CUR readings were compared using descriptive statistics, Wilcoxon signed-rank tests, and MARD calculations.
• Display errors were analyzed for associations with glucose level and rate of change (RoC).

Main Results:

• CUR values were generally comparable to AL (mean difference: -1.2 ± 6.4 mg/dL), with slight underestimation in hypoglycemia.
• Approximately 10% of readings showed discrepancies exceeding ±10 mg/dL.
• Mean Absolute Relative Difference (MARD) was similar for AL (9.7%) and CUR (10.1%), with increased deviation during hypoglycemia.
• Display errors (3.9%) were more frequent at high glucose levels and during rapid RoC (p < 0.001).

Conclusions:

• While generally small, differences between AL and CUR glucose values are systematic and amplified during hypoglycemia and rapid glucose fluctuations.
• These discrepancies can influence the reclassification of readings across clinical thresholds, potentially affecting patient-clinician alignment.
• Understanding these patterns is crucial for accurate CGM data interpretation and optimizing automated diabetes management systems.