Impact of Ascorbic Acid and Exercise on Accuracy of a Glucose Monitoring System with GDH-FAD Technology in Adult Patients with Type 1 Diabetes Mellitus: A Double-Blinded, Randomized Trial

The performance of a new continuous glucose monitoring system (CGM) with flavin adenine dinucleotide-dependent glucose dehydrogenase (GDH-FAD) technology in adults with type 1 diabetes mellitus (T1DM) was assessed, with a focus on the impact of ascorbic acid and exercise on the accuracy of glucose measurements relative to Yellow Springs Instrument (YSI) 2300 control. Adults with T1DM aged 18–65 years using a stable glucose management treatment regimen for at least 3 months with multiple daily injections or continuous subcutaneous insulin infusion participated in this study at a single center. Participants attended a screening visit and three in-clinic visits for frequent blood sampling with blood glucose measurements using YSI measurements as the reference measurement as endorsed by the Food and Drug Administration (FDA). Participants had two meals at each clinic visit leading to pronounced glucose excursions. On the second and third in-clinic visits, participants performed moderate exercise in between the two meals and were randomized to receive 1000 mg of ascorbic acid orally at either of those visits. Accuracy evaluation included the proportion of CGM values within 15% of YSI glucose values > 100 mg/dL or within 15 mg/dL of YSI values ≤ 100 mg/dL (%15/15), along with %20/20, %30/30, and %40/40 agreement rates (AR) across CGM ranges. The mean absolute difference (MAD) and mean absolute relative difference (MARD) with and without ascorbic acid and exercise, as well as their differences, are presented across glucose ranges. Data from 16 participants were analyzed. In the overall CGM range (35–450 mg/dL), the %20/20 AR was 92.0%. The overall changes in MAD between the exercise/nonexercise and the ascorbic acid/nonascorbic acid conditions were −1.3 mg/dL and −1.1 mg/dL. The overall changes in MARD between those two sets of conditions were −1.5% and −1.6%, respectively, none of which were considered to be clinically relevant. There were no serious adverse events. This study provides evidence that neither exercise nor ascorbic acid results in any clinically significant interference on glucose measurements using the iCan CGM system. ClinicalTrials.gov identifier, NCT05348928.