Comparability of Interstitial and Capillary Blood Glucose Values: A Cross-Sectional Study of Samples from Patients...

Several studies have evaluated the use of interstitial flash glucose (IFG) monitors in critically ill patients. IFG offers potential advantages over capillary blood glucose (CBG) measurements. This study examined the agreement between IFG and CBG values in patients with multiple organ failure (MOF) who required vasopressors and were admitted to the intensive care unit (ICU).

This cross-sectional study included 394 pairs of CBG and IFG determinations corresponding to 11 ICU-admitted patients. All patients had MOF and required an IV vasopressor infusion. IFG accuracy against CBG was assessed using the Bland-Altman method and by calculating the median absolute relative difference (MARD). Clinical accuracy was assessed using the Clarke Consensus Error Grid (CEG).

The MARD between IFG and CBG was -4.90 (IQR -18.05 to 9.75) mg/dL. Only 76 (19.3%) glucose pairs had MARD above the recommended value of 14%. A positive cumulative balance and intravenous insulin administration were associated with an increased MARD. Bland-Altman analysis revealed a mean difference of 4.79% (SD = 24.06%, 95% CI 2.34-7.24%), with upper and lower limits of agreement of 51.93% (95% CI 47.0-55.56%) and -42.36% (95% CI -46.7 to -37.9%), respectively. A total of 186 (49.9%) IFG were above the recommended threshold value of 12.5% compared to the CBG reference. Only 246 (62.6%) determinations were in the risk zone of the CEG.

IFG does not demonstrate analytical or clinical accuracy equivalent to CBG in patients with MOF requiring vasopressor infusion.