Defining Glycemic Variability in Very Low-Birthweight Infants: Data from a Continuous Glucose Monitoring System

Background: Glucose variability (GV) is a matter of interest for researches in recent years. It is connected with oxidative stress, which is crucial in the development of multiple complication of prematurity. However, glycemic variability in preterm infants was poorly investigated. This study aims to investigate glycemic variability obtained from a continuous glucose monitoring (CGM) system in a cohort of very low-birthweight (VLBW) infants. Methods: A prospective, single-center, open cohort study enrolled 74 VLBW infants with a mean birthweight of 1066g and median gestational age of 28 weeks. A CGM system (Guardian Real-Time CGM((R)), Medtronic, Northridge, CA) was used to measure interstitial glucose concentration. The glycemic variability was calculated using EasyGV. Results: Most glycemic variability indices in VLBW infants showed log-normal distribution and for these, geometric mean divided by/xgeometric standard deviation (GSD) was calculated: M-value 2.28 (divided by/x1.82), mean amplitude of glycemic excursions (MAGE) 1.89 (divided by/x1.34), average daily risk ratio (ADRR) 2.22 (divided by/x2.56), lability index 0.46 (divided by/x1.71), J-index 0.46 (divided by/x1.71), low blood glucose index 2.05 (divided by/x1.66), high blood glucose index 1.11 (divided by/x2.44), continuous overlapping net glycemic action (CONGA) 5.54 (divided by/x1.16), mean of daily differences (MODD) 1.23 (divided by/x1.38), and coefficient of variation 1.15 (divided by/x1.31). Only SD of glucose concentration showed a normal distribution: arithmetic mean 1.24 (+/-0.37). ADRR, J-index, MODD, CONGA, and MAGE are moderately to strongly correlated with SD. Conclusions: In our cohort of VLBW infants, almost all glycemic variability indices showed skewed positive distribution. The natural central tendency measure for the log-normally distributed data is the geometric mean and for statistical variation is the GSD.