Disagreement between capillary blood glucose and flash glucose monitoring sensor can lead to inadequate treatment adjustments during pregnancy.

OBJECTIVE: Continuous glucose monitoring tends to replace capillary blood glucose (CBG) self-monitoring. Our aim was to determine the agreement between CBG and a flash glucose monitoring system (Flash-GMS) in treatment decision-making during pregnancy. RESEARCH DESIGN AND METHODS: Insulin-treated women with either type 1 (n=25), type 2 (n=4) or gestational diabetes (n=4) were included. A Flash-GMS sensor was applied for 14 days. Women scanned the sensor whenever they monitored their CBG. The primary endpoint was the proportion of discordant therapeutic decisions they would have made based on Flash-GMS rather than CBG results. Glucose averages, mean absolute difference (MAD), mean absolute relative difference (MARD) and Flash-GMS accuracy were also estimated. RESULTS: Data for forty 14-day periods were available. Preprandial Flash-GMS and CBG values were 93±42mg/dL and 105±45mg/dL, respectively (P<10-4), and 2-h postprandial (PP) values were 106±45mg/dL and 119±47mg/dL, respectively (P<10-4). MAD was 14±22mg/dL preprandial and 15±24mg/dL 2-h PP; MARD was 19%; and 99% of glucose value pairs were within the clinically acceptable A and B zones of the Parkes error grid. Concordance rate for therapeutic decision-making was 80-85% according to ADA targets and 65-75% according to a pragmatic threshold. At different time points of the day, 83-92% of discordant results were due to Flash-GMS values being lower than their corresponding CBG values. CONCLUSION: Flash-GMS tends to give lower estimates than CBG. Thus, in cases requiring therapeutic changes to treat or prevent hypo- or hyperglycaemia, 25-35% of choices would have been divergent if based on Flash-GMS rather than CBG.