Comparison of glucose monitoring between Freestyle Libre Pro and iPro2 in patients with diabetes mellitus

Aims/Introduction Flash and continuous glucose monitoring systems are becoming prevalent in clinical practice. We directly compared a flash glucose monitoring system (FreeStyle Libre Pro [FSL-Pro]) with a continuous glucose monitoring system (iPro2) in patients with diabetes mellitus. Materials and Methods Glucose concentrations were simultaneously measured using the FSL-Pro, iPro2 and self-monitoring blood glucose in 10 patients with diabetes mellitus, and agreement among them was assessed. Results Parkes error grid analysis showed that the 92.9 and 7.1% of glucose values measured using the FSL-Pro fell into areas A and B, respectively, and that 96.3, 2.8 and 0.9% of those determined using iPro2 fell into areas A, B and C, respectively. The median absolute relative differences compared with self-monitoring blood glucose were 8.1% (3.9-12.7%) and 5.0% (2.6-9.1%) for the FSL-Pro and iPro2, respectively. Analysis of 5,555 paired values showed a close correlation between FSL-Pro and iPro2 glucose values (rho = 0.96, P < 0.01). Notably, 65.3% of all glucose values were lower for the FSL-Pro than the iPro2. Median glucose values also decreased by 3.3% for the FSL-Pro compared with the iPro2 (177.0 [133.0-228.0] vs 183.0 [145.0-230.0] mg/dL, P < 0.01). The difference in glucose values between the two systems was more pronounced in hypoglycemia. The median absolute relative difference between FSL-Pro and iPro2 during hypoglycemia was much larger than that during euglycemia and hyperglycemia. Conclusions Both the FSL-Pro and iPro2 systems are clinically acceptable, but glucose values tended to be lower when measured using the FSL-Pro than the iPro2. Agreement was not close between these systems during hypoglycemia.